PB 1475

Agricultural Extension ServiceThe University of Tennessee

Introduction 3Types of Grapes 3Site Selection 4Soils 4Propagation 4Planting

Time to plant 5Purchasing vines 6Spacing 6Preplant care 7Planting 7

Pruning and TrainingTerminology 8Trellis design and construction 8Training systems 11Pruning at planting 11Vertical trellis systems:

4-cane kniffin 11umbrella kniffin 14Hudson River umbrella 14bilateral cordon 14

Horizontal trellis systems:Geneva double curtain 16

Pruning bearing vines 16Balanced pruning 16Time to prune 18Trunk renewal 19Pruning neglected vines 19Disposal of prunings 20

Fertilizing and Liming 20Vineyard Floor Management 21Pest Control 23Estimating Yields in Vineyards 23Harvesting 25Storage 26Additional References 26

Grapevine Propagation from Cuttings 1

Grapevine Propagation from Layering 2

Suggested Spacings for Grapevines 3

Planting an Own-rooted Grapevine 4A

Planting a Grafted Grapevine 4B

Vertical Trellis Design 5

High-Head Bilateral Cordon Trellis 6A

Low-Head Bilateral Cordon Trellis 6B

Geneva Double Curtain (GDC) Trellis 7

2-Wire Vertical Trellis 8

End Post and Brace for a Single-Wire Trellis 9

Common Training Systems for Grapes 10

Pruning and Training, First Year 11

4-Cane Kniffin System 12

Vertical Trellis Systems, First Dormant Pruning 13

4-Cane Kniffin System, Mature Vine 14

Umbrella Kniffin System 15

Hudson River Umbrella System 16

Bilate Cordon System, First Dormant Pruning 17

Spur Pruning Grapevines 18

Geneva Double Curtain (GDC) Training 19

New Wood Versus Old Wood on Grapevines 20

Cross Section of a Compound Bud of Concord 21

Trunk Renewal 22

Vineyard Floor Management 23

David W. Lockwood, ProfessorDarren K. Robinson, Assistant Professor

Plant and Soil Science

Several different types ofgrapes are grown in the UnitedStates. Each type has characteris-tics that may make it more or lessdesirable than others in terms ofadaptability and use of the fruit.

American grapes used forfruiting are usually one of twospecies; Vitis labrusca (i.e. Con-cord, Niagara) or Vitis aestivalis(i.e. Norton, Delaware). Americanvarieties tend to be more adaptedto Tennessee growing conditionsthan the other types. Fruit fromthese varieties is widely used forjuice, wine, preserves and freshconsumption.

Several seedless grape variet-ies have been developed. They donot yield as heavily as seededAmerican varieties. However,they do offer potential for freshfruit sales.

Grapes may be grown in all parts of Tennessee. However, not all types of grapes or varieties of grapes are

adapted to all parts of the state. With proper attention to selection of the correct type and variety of grapes, site

selection and reasonable cultural practices, grapes can be a viable crop for both commercial and hobby growers.

The development of commercial wineries and the introduction of several seedless grape varieties adapted to

Tennessee growing conditions have contributed to grape production becoming an increasingly important part of

Tennessee’s agricultural economy.

French-American hybridvarieties are crosses between Eu-ropean varieties and certain wildspecies found in America. Fruitfrom the “hybrids” is used prima-rily for wine. Varieties includeSeyval, Vidal, Foch, DeChaunac,Chambourcin and Chancellor.Many of the hybrid varieties willperform as well as several of theAmerican bunch varieties.

Muscadine grapes (Vitisrotundifolia) grow well in manyparts of the Southeast. Unfortu-nately, cold injury to cordons andtrunks can be a fairly common oc-currence in most parts of Tennes-see. Therefore, commercial mus-cadine grape production is notsuggested for most parts of thestate. Fruit from muscadine vinesis used for juice, wines, process-ing and fresh consumption.

Vitis vinifera (Europeangrape) varieties, such as Chardon-

nay, and Cabernet Sauvignon tendto be less winter-hardy and moresubject to fungal diseases than ei-ther American grapes or French-American hybrids. Expect loweryields and less consistent produc-tion with viniferas than othertypes of grapes. They should onlybe grown in the most desirablesites and with the best culturalpractices. Due to the likely pres-ence of root phylloxera, V. vin-ifera varieties should be graftedonto phylloxera-resistantrootstocks. While test plantings ofviniferas are encouraged, exten-sive plantings are not suggestedfor Tennessee at this time.

Many grape varieties, in addi-tion to those listed above, are alsoavailable. Refer to Extension PB746, “Tree Fruit, Tree Nut andSmall Fruit Cultivars for Tennes-see,” for more suggestions.

diameter1/4” - 3/8”

9”-12”

Diagram 1.GrapevinePropagationfrom Cuttings

While grapes may be grownunder a wide variety of conditions,certain factors may make one sitemore desirable than another.

Areas elevated above their im-mediate surroundings offer someprotection from frosts and dis-eases. Injury to buds or newgrowth due to frost becomes morelikely the closer you get to thebasal part of a slope. Likewise,fogs keep foliage and fruits wet,thus increasing the potential forcertain diseases. By establishingthe vineyard higher up the slope,both frost and disease pressuremay be lessened. The very top of ahill may not be the most desirablespot, however, as wind damageand winter freeze injury are apt tobecome more of a problem.

Direction of slope may havesome impact on vineyard perfor-mance. Vines on a north to north-eastern slope tend to be less proneto winter damage and spring frostinjury than those on a slope withsome southern orientation. Vine-yards on an eastern-facing slopemay have less disease pressurethan on other slopes, since themorning sun dries off fruits andfoliage earlier on the eastern slope,thereby lessening the chances fordisease development.

Grapevines should be plantedwhere they will receive full sun.Shade will cause plants to become“leggy.” These elongated, spindlyshoots will produce fewer fruitingsites with poorer quality fruit thatare more prone to disease prob-lems.

Grapevines can be deep-rootedin certain soils. Ideally, vines needa minimum of 24 to 36 inches ofrooting depth before encounteringan impervious layer, such as rockor a hardpan. The deeper and moreextensive the root system, the morecapable the vine will be to with-stand stresses such as drought, lowfertility and low soil temperatures.

While water is essential forgrowth and production, grapevineswill not tolerate excessive soilmoisture, especially during thegrowing season. Sites with poorinternal and/or surface drainagecharacteristics should either bemodified to solve the problem oravoided. Irrigation is desirable onexcessively droughty soils.Grapes do not require highly fertilesoils. In fact, such soils are unde-sirable, since growth may be ex-cessive, causing shaded, poor-quality fruit and increased diseasepressure. For soils with low tomoderate fertility levels, a limingand fertilization program may bedevised that will give a balancebetween vegetative growth andfruiting. Knowledge of soil charac-teristics before planting is valuablein determining the best vine spac-ing and trellis system to use.

Grapevines may be success-fully propagated by several meth-ods. It may be possible to propa-gate your own plants if existingvines are healthy and if proper pro-cedures are followed. If these crite-ria are not met, rooting success andsubsequent plant growth will be

poor, creating a delay in develop-ing a productive vineyard.

Most grapevines, with the ex-ception of V. vinifera varieties, aregrown on their own roots. V. vin-ifera varieties are especially sensi-tive to root phylloxera, which is athreat throughout the country.Therefore, these vines are graftedonto resistant rootstocks (Dia-grams 4A and 4B, Own-rooted vs.Grafted Vines).

American bunch varieties andFrench-American hybrid varietiesmay be propagated by cuttings.Cuttings should be taken in earlyto midwinter from healthy, well-matured canes. The ideal cuttingsare about 1/4 to 3/8 inch in diam-eter and three to four nodes inlength (Diagram 1). The bottomcut should be made just below thebasal bud. The top cut should bemade about 1 inch above thetop bud.

Cuttings should be groupedinto bundles of uniform lengthswith the top ends together. Bundleeach variety separately. Bundlesmay be moistened, put in plasticbags, sealed and held in refriger-ated storage (keep from freezing)or buried in a trench with the basalends up and covered with severalinches of soil and/or mulch. Thetrench should be well-drained. If aprotective structure such as agreenhouse is available, cuttingscan be set immediately without theneed for storage.

The area in which the cuttingswill be placed should be free ofweeds and worked 10 to 12 inchesdeep. Irrigation is highly desirable.

Once the danger of frost ispast, cuttings may be set in thenursery. Place the cuttings about 6inches apart in the trench, with allbuds except the top one below soillevel. Backfill the trench and firmthe soil around the cuttings.

Keep the nursery rows free ofweeds throughout the growing sea-son. Control of insects and dis-eases is essential to maximizegrowth. Carefully monitor mois-ture levels and water when neces-sary. Fertilization is not needed inmost cases and is definitely notrecommended in the early stagesof growth, as fertilizer burn mayoccur to tender, new roots. If fertil-izer is used during the growingseason, keep it several inches awayfrom the base of the cuttings. Useabout ounce of 10-10-10 fertilizeror its equivalent per linear foot ofnursery row. Do not fertilize aftermid-July.

Cuttings should be held in thenursery row until dormant. At that

Diagram 2. Grapevine Propagation from Layering

3 - 4 buds

time, they may be dug, stored un-der moist conditions at about 34 F.until planting time or transplanteddirectly from the nursery row tothe vineyard at the appropriatetime.

Layering is the surest way topropagate all grape varieties. How-ever, it is seldom used except forvarieties that do not root readilyfrom cuttings, such as with musca-dines and Cynthiana. Layering isalso the preferred technique to fillvacancies in established vineyardswhere vines are growing on theirown roots, since young vines re-main attached to the mother vineuntil well-established.

To layer a grapevine, dig ahole 10 to 15 inches deep wherethe new vine is desired. This loca-tion must be close enough to themother vine so it can be reachedby a long cane. Select a cane onthe mother vine and prune it to alength about 3 feet greater than thedistance between the vine and thehole. Extend the long cane to thebottom of the hole, then bend itvertically upward so that at leasttwo buds remain above the soilonce the hole is refilled.

Strip off developing shoots onthe long cane between the mothervine and the soil. Shoots arisingfrom nodes above the soil line onthe tip of the long cane should beretained. Do not allow the layeredplant to fruit for two years.

Do not separate the layeredvine from the mother vine until thediameter of the trunk of the newvine is greater than that of thewood leading to it from the mothervine. This would indicate theyoung vine has a functional rootsystem and no longer is dependenton the mother vine. (Diagram 2).

Grafting, including budding, isa fairly technical procedure. Thespecific type of graft to be usedwill depend on the size of the vinebeing topworked and the time ofyear in which it will be done. Ad-ditional information on grapevinepropagation may be obtained atyour county Extension office.

Time to plantThe ideal time to plant bare-

root grapevines in Tennessee is inlate winter to early spring (mid-February to early April). Vines

planted in fall or early winter maysuffer root injury or death in theevent of a prolonged cold periodshortly after planting. If plantinglater than early April, hot, dry con-ditions may occur that could re-duce plant growth or even causeplant death.

Since vineyard establishmentcan be fairly expensive, and sincea properly maintained vineyardwill live and fruit for many years,it is very important to purchasehealthy plants of the correct vari-ety. Therefore, purchase plantsfrom reputable nurseries. As longas the vines are properly cared forin the nursery and during shipping,it is not necessary to purchasethem from local nurseries. Vigor-ous, one-year-old plants are best.Once plants are received, take careto prevent roots from drying out,freezing or overheating.

The number of plants neededto supply fruit will vary consider-ably, depending on the use of thefruit and the number of people whowill be consuming it. Calculate thenumber of vines needed based onthe assumption that each matureplant will yield about 15 pounds offruit (25 to 35 pounds for a maturemuscadine vine) and that about 15to 20 pounds of fruit are requiredto give about one gallon of juice.Realize that these figures are onlyrough estimates and that severalfactors may influence them.

Space grapevines about 8 feetapart in the rows. This spacingmay need to be increased to about10 feet for vigorous varieties set onfertile soils, or reduced to 6 feet forweak-growing varieties planted onless-fertile soils. For muscadines, aspacing of 16 to 20 feet apart inrows is suggested. The distancebetween rows will depend on thesize of the equipment being used tomaintain the vineyard, the lay ofthe land (extra distance betweenrows may be needed on steeperslopes) and the type of trellis con-structed to support the vines. Com-mercial grape growers generally

space rows 10 to 12 feet apart. Donot space rows less than 6 feetapart, as mutual shading amongrows may become a problem.(Diagram 3. Suggested Spacingsfor Grapevines). Table 1 shows thenumber of vines needed per acre atseveral in-row and between-rowspacings. To calculate the numberof vines needed per acre, multiplythe distance between vines in arow by the distance between rowsto find the square feet of space foreach vine. Divide this number into43,560 (the number of square feetin an acre) to get the number ofvines per acre.

Diagram 3. Suggested Spacings for Grapevines

American Bunch, French-American Hybrids,V. vinifera and Seedless Grapes

Muscadines

8 - 10 ft. between vines in a row

10 - 12 ft. between rows

16 - 20 ft. between vines in a row

10 - 12 ft. between rows

Inspect vines upon receipt tobe sure the roots have not driedout, frozen or overheated. Healthyroots should feel firm, not spongyor hard and brittle when squeezed.You should be able to bend theroots some without breakingthem. Cutting through the exteriorof a root should reveal white tis-sue. If the interior of the root istan to brown, the roots have beendamaged and plant survival is aptto be poor.

Store vines in a cool area.Take care to prevent the rootsfrom drying out, freezing or be-coming too hot. If properly stored,vines may be kept in the shippingbundle for several weeks beforeplanting.

Soak vine roots in water for acouple of hours prior to planting.Take care to prevent the rootsfrom drying out during planting.

Table 1. Number of Vines per Acre

Distance between rows

8 feet 10 feet 12 feet

Distance 6 feet 907 726 605

betweenvines in 8 feet 680 544 453

a row 10 feet 544 435 363

16 feet 340 272 226

20 feet 272 217 181

v i n e s / a c r e

Example: 8 feet between vines in a row x 10 feet between rows = 80square feet per vine. Divide 80 into 43,560 to get 544.5 vines per acre(round off to 544 vines.)

Inspect the root system before

planting. Prune off broken, dead,diseased or insect-infested roots.Do not prune the root system anymore than is absolutely necessary.

Grapevines propagated fromcuttings or layering should beplanted as deep as they were set in

the nursery. Dig holes deep enoughand wide enough to accommodatethe root system without having tobend roots to fit (Diagram 4A.Planting an Own-Rooted Grape-vine). Grafted grapevines shouldbe set with the graft union justabove the soil line (Diagram 4B).Set the vine in the hole, spread outthe root system and work soil inaround the roots to eliminate airpockets. Once the soil has coveredthe root system, tamp it down tofurther assure good root/soil con-tact. If the soil is dry, pour water inthe hole before completely fillingthe hole. Fill the hole with soil tothe same level or slightly higherthan the surrounding ground. If adepression in the soil is left atplanting, it should be filled beforegoing into the first dormant season.Freezing and thawing of water indirect contact with the trunk coulddamage it.

DO NOT add soil amend-ments such as peat moss, sawdustor manure to the soil being used tobackfill the hole. Such a practice

Diagram 4A. Planting anOwn-Rooted Grapevine

Diagram 4B. Planting aGrafted Grapevine

graft union

rootstock

scion

creates a “flower-pot” effect,which discourages root growth intothe surrounding soil. The more re-stricted the root system of thegrapevine, the more susceptible thevine will be to drought, flooding orimproper fertility. Do not put fer-tilizer in the hole because plantroots may be injured or killed bydirect contact with high amountsof certain fertilizer materials.

Pruning and training are twoseparate practices that play veryimportant roles in the developmentand maintenance of grapevines.They influence light distributionthroughout the canopy, whichgreatly affects yields, fruit qualityand pest problems. Ease of man-agement of the vines and the cropwill be impacted by pruning andtraining practices. Support wireson the trellis should be set at aheight that will make pruning,cluster thinning and harvest moreconvenient.

Early in the life of the vine-yard, pruning and training are usedtogether to build a vine of the de-sired size and shape. Once the vinehas filled its allotted space on thetrellis, annual pruning is used torenew fruiting wood, to promoteuniform light distribution through-out the canopy and to keep thevine from overgrowing neighbor-ing vines. Pruning and training areparts of an integrated vineyardmanagement system in which eachpractice has an influence on thesuccess of all other cultural prac-tices and on the overall crop.

TerminologyArms — major branches of

the trunk on which canes or spursare borne.

Cane — a mature, woodyshoot after leaf drop.

Cordon — extension of atrunk, usually oriented horizontallyalong a wire. Fully developed cor-dons can bear spurs and canes.Cordons may extend in one or twodirections from the trunk. They areretained for several years.

Pruning — removal of partsof a plant. It is done to regulatecrop size and fruit quality. Pruningalso is used to determine the qual-ity, quantity and location of veg-etative growth. The two basictypes of pruning for grapes are 1)cane renewal (cane replacement),in which canes that fruited the pre-vious year are removed and somecanes that grew the previous yearare selected for fruiting in the cur-rent year, and 2) spur pruning,where short canes that fruited theprevious year are removed and re-placed with spurs on the cordon asa site for fruiting and shoot growththe current year. Pruning should bedone every year of the vine’s life.

Shoot — green growth from abud on a cane, spur, cordon, arm ortrunk. A shoot always bears leavesand tendrils and may also bearfruit. In the fall, a shoot maturesand drops its leaves. It is thencalled a cane.

Spur — cane pruned to a fewnodes (five or less). A renewalspur has one or two buds to pro-duce canes at a particular locationon an arm or cordon. A fruitingspur is chosen to produce fruitingshoots.

Training — development ofthe framework of the vine on thetrellis. Training impacts exposureof fruit and foliage to light, as wellas ease of management.

Trunk — the semi-permanent,above-ground, vertically-orientedstem of a vine.

The trellis of a vineyard shouldbe strong, long-lasting and requirelow maintenance. Its purpose is tosupport the foliage and fruit ofvines, thus allowing good light in-terception and ease of manage-ment. Trellis construction repre-sents a major investment in bothtime and money.

Two types of trellises are sug-gested for use in Tennessee vine-yards. The vertical trellis uses twowires. The lower wire is situated at3 feet aboveground to enhancegood air circulation under thevines, and the top wire is at about6 feet aboveground (Diagram 5).The vertical trellis is used for thefour-cane Kniffin system, the um-brella Kniffin system and theHudson River umbrella system.The bilateral cordon system, avariation of the vertical trellis, usesa single wire to support the cor-dons and the crop. This wire maybe 6 feet aboveground for a high-head cordon system where newshoots grow down, or 3 feet inheight for a low-head cordon sys-tem where new shoots grow up.Movable catch wires may be usedto position shoots in either thedownward (Diagram 6A) or up-ward (Diagram 6B) direction. A

Diagram 5.Vertical Trellis Design

3 - 4 ft. 16 - 24 ft.

3 ft.

3 ft.

2 ft.

Diagram 6A.High-Head BilateralCordon System

Downward cane growth form spur buds

Before pruning After pruningCordons

Catch wire

Catch wire

Before pruning After pruning

Upright growing shoots

SpursCordons

Diagram 6B.Low-Head BilateralCordon System

horizontal trellis is used for theGeneva double curtain (GDC) sys-tem (Diagram 7). This system usesthree wires. One wire, attached tothe posts about 3 feet aboveground, is used for trunk support.Two parallel, horizontal wires at-tached to the ends of 4-foot longcross arms secured to posts at 6feet aboveground hold the cordonsor canes.

Descriptions of posts, anchorsand wire needed for trellises reflectthe needs in commercial vine-yards. Limited plantings usingonly a few vines per row may notneed such a heavily constructedtrellis.

Posts should be long-lasting.Wood posts should be treated forin-ground use and should last up to20 years.

Line posts should be at least 8feet long. The posts should be setat least 2 feet in the ground andextend aboveground 6 feet ormore. Line posts should have a topdiameter of 3 inches or more. Theyshould not be spaced more than 24feet apart. Depending on vinespacing, two or three vines may bebetween line posts. Line posts areused to maintain the correct wireheight in rows (Diagram 8).End posts are used to maintainwire height. All wire tighteningand tensioning is done from theend posts, so they need to bestrong. End posts should be at least10 feet long to allow them to be set3 to 4 feet in the ground and stillhave at least 6 feet of postaboveground (Diagram 8). Theseposts should have a minimum topdiameter of 4 inches. Larger end

Diagram 7.Geneva Double-Curtain(GDC) Trellis

16 - 20 ft

4 ft

5 - 6 ft

2 - 3 ft

Diagram 8.2 - WireVerticalTrellis

Diagram 9.End Post andBrace for aSingle-WireTrellis

3 ft

3 ft

3 ft 2 ftPosts 16 - 24 ft apart

3 - 4 ft 3 - 4 ft

5 - 6 ft

450 300

posts are suggested for Genevadouble curtain trellises. The stabil-ity of an end post can be increasedby setting or driving it so theaboveground part of the post isangled away from the vineyardat about 30 degrees from the verti-cal and braced or anchored(Diagram 9 ).

Many types of braces or an-chors can be used. A screw-in an-chor 4 to 6 inches in diameterworks well. The anchor should beset 4 feet away from the base ofthe post and screwed in at a 45-degree angle toward the end postand aligned with the row. The an-chor should go in the ground atleast 4 feet.

The wire suggested to supportthe weight of the canes or cordons,foliage and the crop is a number11, crimped, high-tensile (210,000p.s.i.), steel wire with a class IIIgalvanizing. Lower wires used fortrunk support or for securing theends of canes on some systems canbe of a lower tensile strength.Uncrimped number 11 or 12 galva-nized fence wire works well.

Wire may be secured to lineposts by stapling it with a 1 to 11/4 -

inch fence staple in the top or inthe side 2 to 5 inches below the topor by drilling a hole in the line post2 to 3 inches below the top andthreading the wire through it. Ifusing staples, be sure to not drivethem in tight, as this could weakenthe wire and also prevent tighten-ing and retensioning the wire.

Taut wires are necessary tominimize sagging of cordons orcanes, to reduce development ofcrooked trunks and to promote

good light penetration throughoutthe canopy of the vines. CornellUniversity recommends tensioningthe wire to 250 to 300 pounds.

Many different types of train-ing systems are used in grapes.The following listing outlines con-ditions that might favor the use ofa particular training system (Dia-gram 10):1. 4-Cane Kniffin — use on low-

vigor varieties so canes on theupper wire do not shade those onthe lower wire.

2. Umbrella Kniffin — suggestedfor high-vigor varieties such asConcord, Niagara and Fredonia.

3. Hudson River Umbrella — useon vines having medium to highvigor.

4. Bilateral Cordon — use on vinesof low to medium vigor.

5. Geneva Double Curtain — sug-gested for vines high in vigor.

Regardless of the trellis systemor training system being used,pruning and training of newly setvines is the same. New vinesshould be cut back to a singleshoot. That shoot should be cutback to two buds prior to budbreak to maximize shoot growththe first growing season. If the trel-lis has been constructed at the timeof planting, loosely tie a stringfrom the vine to the lower trelliswire and secure the new shoot tothe string. This is important in de-veloping a straight trunk, whichpromotes a stronger, more produc-tive vine. If the trellis has not been

constructed by planting time, set astake beside the vine and looselysecure the trunk to it as it grows(Diagram 11). If more than oneshoot develops, pinch the tip out ofall of them except the one selectedto be the trunk. Trunk developmentis the prime consideration in train-ing a new vine. For some types ofgrapes that tend to be more suscep-tible to cold injury, having two ormore trunks may be advisable. Onvines grown from rooted cuttings,the second trunk should originateat or below the ground line. Forgrafted vines, the second trunkshould originate above the graftunion. Ideally, the trunks should beof different ages to lessen thechance of cold injury damaging allthe trunks. Trunks should be re-newed about every 15 years. Incases of cold injury, mechanicaldamage or other problems, trunksmay need to be renewed sooner.

4-cane Kniffin systemThe 4-cane Kniffin system

(Diagram 12) uses fruiting caneson both the upper and lower wires.Wires should be 3 feet and 6 feetaboveground to facilitate good air,light and spray penetrationthroughout the canopy. With vig-orous vines, the lower tier of canescan be heavily shaded, resulting inlow production and poor-qualityfruit. Where this problem arises, itis possible to convert to the um-brella kniffin system. If possible,orient rows on the 4-cane kniffinsystem north and south for the bestperformance.

Diagram 10.Common Training Systems for Grapes

Diagram 11. Pruning and Training First Year

Prune to 1 shootwith 2 buds

Loosely tie 1new shoot to avertical stake

4-Cane Kniffin System Bilateral Cordon System

Umbrella Kniffin System Hudson River Umbrella System

Geneva Double Curtain(GDC) System

During the first dormant prun-ing (one year after planting), headthe trunk about 4 inches above theupper trellis wire (Diagram 13).Lateral branching will result fromthe heading cut and canes that willfruit the following year can be se-lected. In some cases, sufficienttrunk growth may occur to allowheading the trunk above the wireduring the growing season. Elimi-nate all flower clusters, as the pri-mary goal at this stage is to de-velop the vine and fruiting will re-duce growth. During the next dor-mant pruning, canes can be trainedto the upper and lower trellis wireson each side of the trunk.

Diagram 12. 4-Cane Kniffin System

3 ft

2 ft

3 ft

8 - 10 ft

Renewal spur

Cane

Trunk

3 ft 8 - 10 ft

Diagram 13.Vertical Trellis Systems First

Dormant Pruning

Pruning mature vines (Diagram14) involves the following steps:1. Remove at the trunk all canes

that bore fruit the previous year(old wood).

2. Select canes that grew theprevious year (new wood) oneach side of the trunk near boththe upper and lower wires andtrain them to the wires. Thesecanes will bear the next fruitcrop.

3. Select four more canes from theprevious year. Keep one on eachside of the trunk for both the

upper and lower wires. Prunethese canes back to two buds.They are called “renewal spurs.”From them, shoots will grow.Some of these shoots will beselected using the above criteriafor fruit production in two years.

4. Shorten the four canes retainedfor fruit production to eight budseach for weaker varieties and 10to 12 buds each for stronger-growing varieties. Thistechnique is an approximationof the balanced pruning conceptsuggested for commercial

Diagram 14. 4-Cane Kniffin System, Mature Vine

Trunk

Before pruning After pruning

Renewal spur

Old wood

New wood

Fruiting cane, 8-12 buds

vineyards. If desired, thebalanced pruning concept,described later in thispublication, may be used formore precisely determining theoptimum bud number.

The umbrella Kniffin system(Diagram 15) is a modification ofthe 4-cane Kniffin system. It is ahead-training system suggested forvigorous varieties where more ofthe fruiting area is exposed tosunlight than would be the case inthe 4-cane Kniffin system.

At planting, vines are handledas previously discussed. The trunkshould be headed about 6 to 12inches below the top wire. Two tosix canes having eight to 15 budseach arising from the head (orheads) of each vine are selected.Each cane is bent sharply over thetop wire and is extended down tothe lower wire, where it is tied.Approximately the same numberof renewal spurs as canes are left.The renewal spurs should be leftnear the head of the vines. Arms atthe head of a mature umbrella-Kniffin are usually kept at least 1foot or more in length.

The Hudson River umbrellasystem (Diagram 16) is amodification of the UmbrellaKniffin system where the armsextend along the top wire halfwayto the next vine. These arms, nowcalled cordons, will live and bearfruiting spurs for several years.Spurs arise along cordons and

Diagram 15. Umbrella Kniffin

Trunk

Renewalspur

Arm

Shoots

Tie shoots to the lower wire

Diagram 16. Hudson River Umbrella

Tie shoots to the lower wire

Cordons

shoots that grow from buds on thespurs are directed verticallydownward and tied to the lowerwire. At pruning, head shoots (nowcalled canes) back to three to fourbud spurs. Remove some spursdirectly at the cordon to stimulatedevelopment of new growthdirectly off the cordons.

Some types of grapes have adownward growth habit, whileother types grow up. The cordon

support wire on downwardgrowing grapes should bepositioned at 6 feet aboveground.The lower wire of the verticaltrellis would serve as a trunksupport wire and a catch wire fornew shoot growth (Diagram 6A).With the upright growing grapes,the wire that will support thecordon should be about 3 feetaboveground. Wires above thislevel may be used as “catch wires”to support new shoot growth(Diagram 6B). Catch wires are

used to position shoots. They aidin maintaining a narrow canopy tofacilitate good light penetrationthroughout the canopy and to keepthe drive areas between rows freeof obstructions.

The developing trunk(s)should be headed to promotelateral branching about 4 to 6inches below the trellis wire thatwill support the cordon (Diagram17). A single shoot should betrained to this trellis wire in eachdirection from the trunk to within

about 12 inches of the shoot on theadjacent vine. This shoot will beretained for several years and willbe referred to as a cordon insubsequent years. Cordons shouldbe renewed every six to eightyears.

Annual pruning of maturevines trained to this system(Diagram 18) involves eliminationof old spurs and canes andselection of new shoots to bepruned back to spurs arisingdirectly from the cordons. Forupright-growing grapes, developthe spurs on the upper 180 degreesof the cordon (Diagram 6B). Fordownward-growing grapes, select

Diagram 18. Spur Pruning Grapevines

Diagram 17.Bilateral Cordon SystemFirst Dormant Pruning

Head trunk4 - 6 inchesbelow thecordon wire

Before pruning After pruning

Space spures 6 to 8 inches apart

Leave 2 to 4 buds per spur

Remove older spurswhenever possible

Diagram 19. Geneva Double Curtain (GDC) Training

4 ft

5 - 6 ft

8 - 10 ft

4 - 5 ft

spurs in the lower 180 degrees ofthe cordon (diagram 6A). Spacespurs 6 to 8 inches apart on thecordons. Do not develop a spur atthe bend of a cordon between thetrunk and the wire, as it will tendto be overly vigorous and shade

adjacent spurs. Shoots to be usedfor spurs should be pruned back totwo to four buds in length,depending on grape variety. Insubsequent years, if new shootsgrow directly off the cordons,develop some of them into spurs

and prune off adjacent older spursat the cordon.

The number of spurs, thedistance between spurs and thenumber of buds left on each spur atpruning depends on the type, thevariety and the vigor of the grape.

Geneva Double Curtain (GDC)When properly maintained, the

Geneva Double Curtain system(Diagram 19) exposes more fruitand foliage to sunlight than manyother systems. It covers a greaterpercentage of land area withfoliage and fruit than other trainingsystems. GDC offers a way todouble the cordon length per vine,while maintaining good sunlightexposure throughout the canopy, areal benefit for vigorous varieties.Two trunks may be developed pervine, with each trunk being trainedto opposite cordon wires, or asingle trunk can be split below thelow wire by heading the trunk 6 to12 inches below the wire and thentraining shoots arising on the trunkto opposite wires. These wiresshould be 4 feet apart to allow forsunlight penetration between thecanes or cordons trained on themthroughout the growing season.When each trunk reaches theappropriate wire, it should beheaded to encourage lateral shootdevelopment. One shoot should betrained in each direction. For lessvigorous varieties, train vines toalternate sides and develop onlytwo cordons per vine.

Cane renewal (canereplacement) or spur pruning may

be done on the wires. Annual canerenewal pruning involvesremoving those that bore theprevious year’s crop, selectingcanes arising on the trunk near thewire and training one of them ineach direction on the wire for thenext crop. These canes will need tobe adjusted for bud number. Selecttwo more canes arising near thepoint where the trunk intersects thewire and prune them back to twobuds. These “renewal spurs” willbe the source of new shoots, someof which will be selected for fruitproduction the following year. Ifvines are to be spur-pruned,cordons will be developed on thewires in the same manner asdescribed for the bilateral cordonsystem. Select 10 to 12 equallyspaced, downward-growing, shortshoots and prune them back tospurs from which fruit and shootswill develop. As with the bilateralcordon system, spurs that bore fruitshould be removed and new shootsarising directly from cordonsshould be selected for pruningback to spurs each year.

Regardless of the trainingsystem and trellis used, the stepsused in pruning mature grapevinesare similar:1. With the exception of trunks and

possibly cordons, remove allwood that is older than one year.

2. Select canes or spurs for nextyear’s crop and for renewalspurs. Remove all others.

3. Adjust the length of remainingcanes or spurs to the desirednumber of buds.

Once an area on a cane or spurhas fruited, it will never fruit inthat same region again. Instead,future yields will be borne onlateral shoots and extensiongrowth. Therefore, regardless ofthe type of pruning conducted, animportant goal is to remove oldwood that has already fruited andto select canes or spurs arisingdirectly off the trunk, renewalspurs or cordons for the next crop.The further clusters develop awayfrom the main framework of thevine, the poorer the size andquality of the clusters will be andthe thicker the canopy will be, thuslimiting light, air and spraypenetration throughout the canopy.New canes to be selected forfruiting have smooth bark that isoften bronze-colored, withprominent buds. Older wood willhave gray, shaggy bark and nobuds (Diagram 20).

The objective of pruning is toobtain consistently large crops ofhigh-quality fruit. Perhaps the keyword in this statement is“consistently.” How much pruningshould be done varies with grapevariety, soil type, fertilizerapplications, water and severalother factors. The balancedpruning concept was developed byresearchers at Cornell Universityto aid in attaining this objective.

With balanced pruning, agrapevine is pruned back, leavingthe maximum number of budssuggested for that varietydepending on its growth theprevious summer. The prunings

Diagram 20. New Wood versus Old Wood on Grapevines

Gray, shaggy bark and no visible buds

Prominent buds, smooth bark (often bronze color)

New Wood (Canes)

Old Wood

Table 2Number of buds to retain for fruiting

Grape variety First pound of Each additional pound Maximum number of buds cane prunings of cane prunings per vine at 8 ft. spacing

American Bunch- Concord 30 plus 10 60 Fredonia 40 plus 10 70

Niagara 25 plus 10 60 Delaware “ ” “ Catawba “ ” “

French-American hybrids - Small-clustered varieties such as Foch and Leon Millot 20 plus 10 50

Medium-clustered varieties such as Aurore, Cascade and Chelois 10 plus 10 40

Large-clustered varieties such as Seyval, DeChaunac and Chancellor 20 plus 10 45

Vinifera varieties (prune after growth 20 plus 20 60

has begun)

that grew the previous year areweighed and this figure is thenused to refine the number of budsto be left. For example, accordingto Table 2, Concord should have amaximum of 60 buds on vines set8 feet apart. For the first pound ofcane prunings, 30 buds should beleft. For each additional pound ofprunings, 10 more buds should beleft, up to a maximum of 60 buds.While weighing prunings soundslike a tedious undertaking, it won’t

take long before you can estimatepruning weights and foregoweighing on a regular basis. Besure to weigh only the pruningsfrom the previous year’s growth.

Overcropping, which may alsobe regarded as underpruning,results in small clusters and smallberries. High levels of shade willresult in poorer-quality fruit andincreased pest pressures due topoor light, air and spraypenetration. Vines weakened bythe excessive crop become moresusceptible to cold injury and maynot initiate enough fruit buds forthe next year’s crop.

Overpruning (undercropping)leaves too few buds to give a goodcrop. Bull canes (very vigorouscanes) are more susceptible to coldinjury than canes growing at moremodest rates. The high vigorcauses heavy shading, with aninevitable decrease in fruit qualityand increase in pest pressure. Also,since the distance between budsincreases with increasing canevigor, it may be impossible toretain the desired number of budswhile keeping canes within theirallotted space.

Weak vines should not beallowed to carry a heavy crop, asfruiting can be an exhaustiveprocess. It is advisable to retain atleast 15 to 18 nodes on a weakvine and then remove all clustersas soon as they begin to develop,as opposed to pruning vines backto just a few nodes.

Pruning in fall may interferewith the vine’s ability to harden offproperly, thus increasing thepotential for winter injury. Theoptimum time to prune grapevinesis in late winter to early spring.When done at this time, vines will“bleed.” Bleeding is notdetrimental to vines. Pruning inlate winter to early spring enablesyou to assess the extent of coldinjury and prune it out.

Delayed pruning involvespruning after growth has started.Bud break begins on the ends ofcanes first and progresses towardthe trunk. With both canereplacement and spur pruning, aportion of the cane will need to beremoved to adjust bud number. Bywaiting to prune until 4 to 5 inchesof new growth are present on theends of canes, bud break in thearea where fruiting is desired canbe delayed by 10 to 14 days. Thismay be of merit in avoiding injurydue to a late frost.

Double pruning may be usedwhen time constraints in springwon’t allow delayed pruning. Itinvolves pruning out excess canesprior to bud break. Those to beretained for fruiting are either leftalone or not pruned as far back asthe ideal bud count would require.Then, after the remaining caneshave attained 4 to 5 inches of newterminal growth, they should bepruned to the correct length. Budbreak in the desired area will bedelayed as a result.

If pruning is done before budbreak, it is important to know howfruitful the variety is on secondary

buds to determine how close to thedesired bud number to prune.Frosts or freezes may destroy aportion of the primary buds,leaving varieties that are not highlyfruitful on secondary buds with thepotential for a light crop. Withvarieties like Seyval, which tend tobe quite fruitful on secondarybuds, it is possible to prune to thefinal desired bud number. Forvarieties that are not highly fruitfulon secondary buds, it may beadvisable to leave 50 percent morebuds than needed, in case coldinjury reduces the number ofsurviving buds after pruning. Ifthis is done and no bud kill occursfollowing pruning, vines shouldeither be pruned again or clusterthinning must be used to adjustfruit load to the proper level.

Grapes have compound budsmade up of primary, secondary andtertiary buds. The primary bud willbreak first and will have thegreatest yield potential. It is alsothe bud most likely to be killed byspring frosts. If this should occur,the secondary bud will break andgive rise to new shoots andblooms. Many grape varieties willproduce a substantial crop fromsecondary buds. Most Americanvarieties are not highly fruitful onsecondary buds; however, several,but not all, French-Americanhybrid varieties are. Cayuga Whiteis an example of a hybrid varietythat is not highly fruitful onsecondary buds. If the secondarybuds are also killed, the tertiarybuds may break and give rise tonew vegetative growth. No grapevarieties are fruitful on tertiarybuds (Diagram 21).

Damage to trunks by freezing,equipment contact, insects,diseases, etc. may lessen vineproductivity over time. Trunkrenewal will offset this problem. Itis advisable to renew trunks onvines at least every 12 to 15 years,and perhaps more frequently whereproblems have occurred.

If a sucker arises at the base ofa vine, do not prune it off. Instead,secure it to the trellis wires to keepit growing straight. Use the sametraining method as was employedin new plantings. Once the trunkhas reached an acceptable height,cut off the old trunk during thedormant pruning and develop newcanes from the replacement trunk(Diagram 22).

For vines with multiple trunks,stagger the time that trunks arerenewed to reduce fluctuations incropping. Also, since different agetrunks may differ in theirsusceptibility to cold injury, theeffect of this problem may be lessdevastating.

Diagram 21. Cross section of compound bud of Concord grape

In some instances, vines thathave been neglected for a period ofyears can be restored to aproductive condition. However, ifthe period of neglect has been toolong or if the vine has a lot ofdead, diseased or insect-infested

wood, it may be better to destroythe old vine and plant a new,healthy vine. If the variety isunknown or no longer available, itmay be possible to propagate newvines by taking cuttings or layeringthe old vine. Information of thisprocedure is given in the sectionon “Propagation.”

Several characteristics arecommon with neglected vines.Fruit-bearing wood developsfurther away from the trunk.Neglected vines may have a fairamount of dead wood. They willfrequently have more than onetrunk. Several steps should betaken when pruning such a vine.

First, remove any large, deadcanes or cordons. This will make iteasier to identify those that may beretained.

Second, inspect the trunks. Ifpossible, cut off one or more of thetrunks at ground level and removethem from the trellis. This will

1. Primary bud 2. Secondary bud 3. Tertiary bud 4. Lateral shoot 5. Leaf scar

renewal trunk

Secure new cane and head it at the trellis wire.

Remove the damaged trunk, replacing itwith the new one. Prune to one cane on thenew trunk. Spur prune the following year.

1 2

4

3 5

Retain older trunks, allow new cane todevelop into a third trunk.

Leave one new cane.

Diagram 22. Trunk Renewal

make decisions concerning the restof the vine easier. Also, cutting alive trunk off at ground level mayincrease chances of getting asucker to grow from below groundlevel. This sucker may bedeveloped into a replacementtrunk.

If healthy canes exist close tothe trunk, cut off the cordons onthe trellis wires and train the canesto the wires. Prune them back tothe desired length. If no newhealthy canes exist, select the bestcordon on each side of the trunkfor each trellis wire. Remove allother cordons. Spur-prune thecordons that are being retained.Develop canes closest to the trunkto replace cordons during the nextdormant pruning.

Several years may be neededto renovate a vine that has beenneglected. The overall objectivesshould be to eliminate dead,diseased or insect-infested wood,to gradually renew trunks andcordons and to develop the fruitingwood close to the trunk.

Once the vine has beenrenovated, annual pruning isessential to keep it productive.

Prunings can either bechopped on the vineyard floor orremoved form the planting. A flailmower can chop prunings intovery small pieces and place themin contact with the soil, where theypresent very few problems with thecarryover of insects or diseases.Rotary mowers do not chopprunings fine enough to reduce thereinfection or reinfestation

potential from diseased or insect-infested wood. If prunings areremoved, do not stockpile themnear the vineyard, as they willserve as a source of pest problemsthat will spread back into thevineyard. Burning prunings isprobably the best way to deal withthem, since it will eliminate insectand disease carryover problems.

Grapevines will grow and fruitsatisfactorily over a pH range of5.5 to 7.0. Since the vines will bein place for many years and sinceit is difficult to modify the pH ofthe subsoil after planting, soiltesting prior to planting is highlyrecommended. In a preplantsituation, take a sample in theupper 8 inches of soil and a secondsample at the 8- to 16-inch depth.If lime or nutrients are needed inthe subsoil area, incorporate themat the recommended rates prior toplanting.

For established vineyards,nitrogen may be the only elementneeding application on an annualbasis, especially if attention waspaid to the preplant soil testrecommendations. Applyammonium nitrate at the rate of 0.3lb. or the equivalent in nitrogenfrom another source per vine in anarea extending from 4 to 6 feet outfrom the trunk. If another fertilizeris to be used, be sure to make thenecessary rate adjustment basedupon the actual nitrogen content ofthe fertilizer. The amount ofnitrogen may be adjusteddepending on plant performanceand cropping history in preceding

years. Low rates of fertilizationmay result in inadequate growth tosupport the plant and thedeveloping crop. High rates willpromote excessive growth and toomuch shade in the fruiting zone ofthe vine. The result will be poor-quality fruit and high diseasepressure. Nitrogen applicationshould be made in late winter toearly spring prior to theresumption of growth.

Magnesium deficiency mayoccur in some vineyards. It appearsas an interveinal chlorosis(yellowing of the leaf tissuebetween the leaf veins) beginningfirst on the basal leaves andprogressing upward toward theyounger leaves. The appearance ofmagnesium deficiency close toharvest is not a cause for alarm.However, if the problem shows upearlier in the growing season, stepsshould be taken to correct theproblem. If the soil pH is below5.5, an application of dolomiticlimestone may correct theproblem. Where the soil pH isabove 5.5, consider sprayingmagnesium sulfate (epsom salts) atthe rate of 16 lb. per 100 gallons ofwater using 200 gallons of sprayper acre in each of two post-bloomsprays.

Information and suppliesregarding soil testing are availableat your county Extension office.Assistance in interpreting results ofthe soil test, if needed, may beobtained there as well.

Weed control is an essentialstep in optimizing quality grapeproduction and ensuring the long-term health of both the commercialand home vineyard. Grass weeds(like crabgrass and bermudagrass)and broadleaf weeds (likedandelion) compete heavily withthe vines for growth requirements(such as water and nutrients).Controlling weeds under the vinesdirects the resources to the vines aswell as facilitating good airdrainage and eliminating sites forpest problems to develop. Weedcontrol in the vineyard is bestachieved by adopting a vineyardfloor management program,including a continuous strip devoid

of vegetation under the vines plusa mowed sod strip between therows and around the perimeter ofthe vineyard (Diagram 23.)

Each aspect of thismanagement system providescertain benefits that optimizes thelong-term health of the vineyard.Under the vines, maintaining thearea devoid of vegetation providesthe following benefits:1. Elimination of competition from

weeds for moisture andnutrients, thereby achievinggreater growth rates, especiallyin new vines.

2. Minimize vole damage bypreventing the buildup of amulch layer under the vines.Grape vines can be damaged orkilled by voles feeding on theroots and stem. Meadow voles,found in the northeastern part of

Tennessee, and prairie voles,found from the CumberlandPlateau west, live and feed onthe top of the ground in themulch layer. Thus, maintainingthe vegetation-free stripeliminates protective cover,discouraging voles frominhabiting the area. Pine voles,which are found throughout thestate, work underground, andtherefore are not as easilydiscouraged. Firm, bare soilunder vines will lessen theiractivity.

3. Minimize frost events. Firm,moist, bare soil absorbs moreheat during the day than anyother ground managementsystem. Heat is reradiated fromthe soil at night over a longertime than with other floormanagement systems, thus

Diagram 23. Vineyard Floor Management Program• 10 to 12 feet between rows• 4-foot wide strip under vines free of vegetation• 6 to 8-foot wide sod strip between rows

4 ft.

6 - 8 ft.

10 - 12 ft.

providing some additionalprotection from frost events. Inaddition, the absence ofvegetation allows for improvedcold air drainage, providingadditional frost protection.

4. Minimize insect and diseases bylessening alternate host sites.Certain weeds provide analternate host site for pests ofgrapes so their absence couldresult in a lessening of pressurefrom certain pests in thevineyard. The potential forproblems with grape root borercan also be lessened byremoving many of the egg-laying sites that weeds undervines provide. In addition, thepresence of weeds decreases airmovement, creating humiditypockets favorable for thedevelopment of certaindiseases.On sloping land, rows should

be planted across slopes ratherthan up and down slopes.Maintaining a sod strip betweenrows provides the followingbenefits:1. Serves as a diffusion and

deceleration strip for runoffwater, thereby minimizing soilerosion.

2. Supports equipment movement,especially in wet conditions.

3. Minimizes frost potential whenclosely mowed, as drainage ofcold air is less restricted.

4. Minimizes vole habitat whenclosely mowed.

Between rows, a grass sod isprobably the most desirable type ofground cover, since certainbroadleaf ground covers and/or

weeds may serve as an alternatehost to pests. Thus, grass sod ispreferred. Ideally, the grass sodshould be non-competitive,requiring minimal mowing. Thefine fescues (red and hard fescue)are the least competitive, requiringless mowing compared to tallfescue. They also go dormantduring the heat of the summer.However, seed for these grasses ismore expensive than tall fescueand slow to establish (fall is theoptimum establishment time),thereby leaving vineyard floorssusceptible to erosion duringestablishment. Tall fescue is thedominant grass cover in mostTennessee vineyards.

Tall fescue seed is relativelyinexpensive, readily available andquick to establish (if it is notalready established in the site).Tall fescue supports equipmenttraffic well. However, tall fescue iscompetitive for water and nutrientsand requires more frequentmowing during the growingseason. If not controlled, it willprovide favorable habitat for voles.

This vineyard floormanagement program can beachieved by following a few easysteps. Keep the sod mowed shortbetween rows and around theperimeter of the vineyard. Withinthe row, maintain a 4-foot widestrip (2 feet each side of the vine)under the trellis free of vegetation.Weeds (broadleaves and grasses)can be controlled by mechanicalmeans or with herbicides. Shallowcultivation under the vines can beused for control of annual weeds.In cherty soils, grape hoes or

rotovators may cause damage tothe vines. Cultivating clay soilswhen they are too wet may resultin formation of a shallow,compacted layer (or plow pan) thatwill limit root growth and restrictwater movement to the roots. Inaddition, cultivation is also time-consuming and expensive.Herbicides provide the easiest,least expensive and most effectivemethod of controlling annual andperennial weeds. Herbicides aresafe when used properly, includingbeing applied at the right amountsand the right times. Always readand follow the use directions forthe herbicide product on theproduct label. Choice of herbicideand application timing may bedependent on the size of thevineyard being maintained.

Many herbicide selections areavailable for commercial vine-yards. The best option may be acombination of herbicides. No oneherbicide, applied one time at therecommended rates, will give year-long control. Thus, for season-longcontrol, the best approach is twoapplications per year, using acombination of a non-selectiveherbicide (to control existingweeds) plus preemergence orresidual herbicides (to slow the re-emergence of weeds). The idealprogram includes an application inearly winter (November -December) followed by a secondapplication of a different herbicidecombination (to limit developmentof herbicide-resistant weeds)applied in early summer prior toextensive vine growth that mayinterfere with with uniform

application. For specific herbicideoptions, contact your countyAgricultural Extension office orconsult University of TennesseeAgricultural Extension Servicepublication PB1197, “CommercialSmall Fruit Spray Schedules”.This publication is revisedannually as herbicide products anddirections for use change often.

In summary, vineyard floormanagement is more than justweed control. It is a vital part of anintegrated vineyard managementprogram that aids in optimizing theproduction of quality grapes andensuring the long-term health ofeither the home or commercialvineyard.

Grapevines are vulnerable toattack from many pests. For mosttypes of grapes, a spray program isnecessary to produce fruit ofacceptable quality and to maintainvine health. Two University ofTennessee Agricultural ExtensionService publications, PB1622,“Disease and Insect Control inHome Fruit Plantings,” andPB1197, “Commercial SmallFruit Spray Schedules,” offertimely information concerning pestcontrol in grapes and other fruitcrops. These publications areavailable without charge at yourcounty Extension office. Whenusing pesticides, exercise cautionand always follow label directions.

Many cultural practices willinfluence pest problems invineyards. If possible, select a sitethat is more elevated than theimmediate surroundings. This will

lessen the potential for frost injuryand disease development. Factorsfavoring good air movementthroughout the vineyard andsunlight penetration throughout thecanopy of the vines, such as hightrellises and good pruningpractices, are invaluable forreducing pest pressures andincreasing fruit quality. Properfertilization practices to avoidweak vines or excessive growthrates will aid in avoiding pestproblems. Vineyard sanitation,including raking leaves,elimination of mummified fruitand removal of prunings willlessen pest pressures the followinggrowing season.

Birds have become a majorpest problem in many home andcommercial vineyards. Resultsusing aluminum pie panssuspended in the vineyard andplastic snakes on the vines, as wellas several other practices, havebeen erratic. Netting the vines isthe only sure way to keep birdsaway. Nets should be put on beforebird pressure gets heavy. The netshould completely enclose thevines and either be tied under thevines or anchored to the ground toprevent birds from getting under it.If possible, suspend the nettingabove the vines, possibly byextending another wirehorizontally above the vines. Thiswill keep the vines from growingthrough the netting. With care,netting can last for several years.

Yellow jackets, bees andwasps do not reduce yields verymuch. However, they do causeproblems during harvest.

Insecticides that may be effectiveagainst them have a relatively longwaiting period followingapplication. Therefore, they cannotbe used shortly before harvest.Removal of damaged fruit fromthe vineyard before these pestsbecome a problem helps to reducethe intensity of the problem.Harvested fruit should not be leftsetting in the vineyard, as bees andwasps will be attracted to it.Elimination of nests prior to fruitripening may reduce activity in thevineyard. However, location anddestruction of the nests may bevery difficult.

Having a fairly accurateestimate of yield prior to harvestenables growers to makemarketing arrangements for theircrop. It helps winery managers toknow whether they will have asufficient supply of fruit from theirregular growers or if they will needto investigate other sources ofgrapes for the upcoming crush.Early crop estimates can be usedby growers to determine if vinesare being overcropped orundercropped. If estimates aredeveloped early, cluster thinningmay be used to lessen the stress ofovercropping.

Yields will vary from year toyear due to environmental factorsand cultural practices. Therefore,crop estimates should bedeveloped annually. The accuracyof the estimates will be determinedby the numbers used in making thenecessary calculations. Since

weather conditions, pest pressuresand other factors will influence thedevelopment of the crop followingthe time that estimates are made,expect some differences betweenthe estimates and the actual yield.Using accurate, preciseinformation wherever possible indeveloping the estimates willincrease the reliability of the cropestimates.

Developing accurate cropestimates involves a thoroughknowledge of the vineyard andgrowing conditions plus anaccumulation of information fromprevious years. Crop estimates arebased on good records of averagecluster weights at harvest, anaccurate count of the current livingvines in an acre or block, and an

accurate determination of theaverage number of clusters pervine at the time the estimate isbeing made.

Factors influencing clusterweight include:• flowers per cluster• berries per flower (percent fruit set)• seeds per berry• weight of fruit per seed

Variations in cluster weightare influenced by the percent offlowers that set. Cloudy, rainyweather during or immediatelyfollowing bloom, poor vinenutrition and foliar damage frompests all will result in reducedcluster weights.

The number of clusters on agiven area will vary from year toyear depending on:• number of vines (vine loss over

time)• number of nodes per vine

(dormant pruning severity)• number of shoots per node

(varies with variety, vine vigorand the amount of shoot thinningused

• clusters per shoot (affected byvariety, degree of bud injury,growing conditions for the vineduring the previous growingseason. Shoots growing in heavyshade are more likely to havenodes with less fruitful shoots thefollowing year.

Use the formula below to estimate yield:Estimated Yield (pounds)/vine = (# of clusters/vine) x (average cluster weight)

To get the yield estimate for several vines, simply multiply the estimated yield per vine by the numberof vines.

Commercial growers will want to modify the formula as shown below to get an estimate of tons per acre:Estimated Yield (tons/acre) = (# bearing vines/acre) x (clusters/vine) x (average cluster weight in pounds)divided by 2000.

Clusters/vine may either be counted or calculated by multiplying the number of shoots per vine by thenumber of clusters per shoot.

The number of bearing vines per acre may be calculated using the following formula:

(in-row spacing x between row spacing)Bearing vines/acre = ------------------------------------------------- - missingvines in the acre

43,560 (square feet in an acre)

or use the following chart if the vine spacings in your vineyard are listed:distance between vines distance between rows vines/acre6 feet 10 feet 726

12 feet 6058 feet 10 feet 545

12 feet 45410 feet 10 feet 436

12 feet 363

Be sure to subtract the number of missing vines in the acre to give a more precise yield estimate.

The number of clusters pervine may be calculated bymultiplying the number of shootsper vine by the number ofclusters per shoot. The reliabilityof the average cluster per vinecount increases as more vines areincluded in the count.

Crop estimates can be madeany time after all the flowerclusters are exposed on adeveloping shoot. However,waiting until after fruit set enablesyou to calculate percent berry set,giving a more accurate count.

Vines to be used in makingcluster counts should be selectedthroughout the planting. The morevines that are counted, the moreaccurate the count will be. Howmany vines to count will dependon the size of the vineyard and theuniformity of the vines. For a one-to two-acre vineyard with vines ofa uniform age, size and trainingsystem, only 10 to 15 vines mayneed to be sampled. In a largervineyard where the vines may notbe uniform, separate the vineyardinto several uniform blocks andmake counts from each block.

Average cluster weightshould be determined at harvesteach year. This number shouldthen be included in an average forall the years in which clusterweights have been recorded.Determine the average clusterweight for each variety and eachblock for all the years over whichdata has been obtained. The moreyears involved in developing theaverage, the more accurate theaverage will be. Instead ofrandomly selecting clusters to be

weighed, select the vines, countthe number of clusters on the vine,harvest the fruit and weigh it,being sure to subtract the weight ofthe container. Then calculate theaverage weight per cluster for thatvine.

Factors between sampling timeand harvest (i.e. amount of rainfall,pest pressure, bird damage, deerdamage, etc.), are not constantfrom year to year. Therefore, usingaverages calculated from just oneyear’s crop can be misleading.

Estimates of yield are just that— estimates. Hopefully, theestimate you arrive at will bewithin 10 to 15 percent of theactual yield. The following tipswill help to increase the accuracyof the estimates:1. Accumulate average cluster

weight data over a period ofyears instead of just one year.Actual cluster weights fromeach harvest should be figuredinto the average.

2. Develop cluster weights fromyour own vineyard. Do not relyon those from other areas.

3. Sample the entire vine to get theaverage cluster weight for thatvine.

4. Divide non-uniform blocks intosmaller, uniform sub-blocks andsample each of them separately.

5. Sample each variety separately.6. The same person should develop

crop estimates each year tofurther reduce variation.

Grapes will not increase incolor or sugar level after harvest,so it is essential to allow them toattain the desired level of maturityprior to harvest. Berry color shouldnot be used as an indicator ofmaturity, since the color changecan occur well in advance ofripening.

As grapes ripen, the sugarlevel of the berries will increase,juice pH will increase and totalacidity will decrease. The seedswill turn from green to brown andwill separate easily from the pulp.The stem of the cluster will turnbrownish and become slightlywrinkled.

The best time to harvest willdepend on the intended use for thegrapes. For jelly, grapes should bepicked somewhat early to get alight, clear jelly that will be free ofcrystals. Table grapes are pickedwhen seeds have turned brown andflavor is at its peak and beforeclusters begin to shatter (berriesstart to drop). Wine grapes shouldbe harvested when sugar levels,juice pH and total acidity havereached desired levels. Theselevels may vary depending on thetype of wine to be made.

Uneven ripening of entireclusters or of berries in clustersmay be a problem some years.Weather stresses such as frosts orfreezes may damage some primarybuds (Diagram 21). In manyvarieties, secondary bud break willoccur after clusters from primarybuds have already started todevelop. When clusters from theprimary buds are ready to be

harvested, clusters from thesecondary buds will still be green.These immature clusters shouldnot be placed in containers withthe ripe fruit, as they will reducethe quality of the juice.

Uneven ripening within theclusters of Concord grape is avarietal trait that becomes morenoticeable in hot weather. Thevariety Sunbelt is being suggestedfor planting in areas where unevenripening in Concord has been aproblem.

Fruit should be harvested byclipping or cutting the stem of thefruit cluster. Pulling the clusterfrom the vines may cause grapes tofall from the cluster (shatter). Onceharvested, fruit should not beallowed to get hot. Put it in theshade or in a cooler.

Most grape varieties grown inEastern states cannot be stored forvery long periods of time. As arule, red varieties store longer thanblue-black or white varieties.The ideal conditions for grapestorage include temperatures of 30to 33F and relative humidity of 85to 90 percent. Refrigeratorsgenerally run about 40F and at lowhumidity levels. While thistemperature is close to ideal,moisture loss from the fruit will beexcessive if the fruit is not sealedin plastic bags.

PB 746 Tree Fruit, Tree Nut and Small Fruit Cultivar Recommendationsfor Tennessee

PB1622 Disease and Insect Control in Home Fruit Plantings

PB1197 Commercial Fruit Spray Schedules

Factsheet SP307N Selecting Quality Grapes

Factsheet SP277J Black Rot of Grapes

PB1475-4M-03/01E12-5215-00-005-01

The Agricultural Extension Service offers its programs to all eligible persons regardless of race, religion, color, national origin, sex, age, disability or veteran status and is an Equal OpportunityEmployer. COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS. The University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and

county governments cooperating in furtherance of Acts of May 8 and June 30, 1914. Agricultural Extension Service, Charles L. Norman, Dean