Perennials Produced As Bedding Plants

Karen G. Shedron

Thomas C. Weiler

Department of HorticulturePurdueUniversityWest Lafayette, IN

INTRODUCTION

Perennials are providing the "new" look inlandscapes. Naturalistic flower beds of perennials offer subtle variations in color and foliar

pattern during the season. They thrive for anindefinite number of years, but die to theground every year; they have annual stemsand perennial rootstocks.

During the first growing season after a springsowing many perennials produce only vegetative growth, but flower the second and eachsubsequent year of the plant's life. Since thehome gardener usually demands "instantcolor," perennials for the bedding plantmarket must be grown in such a way that theplants flower the same season they are purchased by the consumer.

Nurserymen provide field-grown plants startedfrom seed or transplants in the spring preceding the year of purchase. After a summer ofvegetative growth, the plants are dug up inlate fall. By this time the top growth is deadand only the crown and roots remain. Theseare then packed in boxes and placed in largecoolers at -3°C to 1°C until spring. In preparation for shipping to retail centers, the crowns,still devoid of leaves, may be individuallyplanted in small plastic bags of soil withcrowns remaining exposed at the top of thebag. Each bagged plant is then placed in itsown open-top box with a color picture of itscharacteristic foliage and flower. Bare-rootplants may also be planted by garden centersfor late spring sales. Several leaves may havesprouted by the time of purchase, and plantsmay or may not display a flower bud. Thismethod of production is very successful; however, such plants are larger than flattedbedding plants.

A few producers have used greenhouses orcold frames for an alternative productionscheme. Containerized perennials are startedduring summer months in the greenhouse andare overwintered at 35-40°F in hotbeds, polyethylene-covered houses, or microfoam-cover-ed beds. Plants are sold in spring either green

or in bud after a flush of new vegetative growthstimulated by raised temperatures and naturally lengthening photoperiod.

The objective of this research was to explorethe environmental requirements for growthand development of four perennial species andto develop a cultural scheme for production ofcontainerized bedding plants. Highly popularspecies were selected: columbine [Aquilegia xhybrida], Shasta daisy [Chrysanthemum xsuperbum], basket-of-gold [Aurinia saxatiiis],and lupine [Lupinus 'Russell Hybrid').

RESULTS

Seeds of each species were germinated andgrown to various sizes in a 65°F night temperature greenhouse using standard practices.These plants were cold-stored and/or treatedunder several daylengths. More completeresults will be available elsewhere, but thefollowing isa summary ofthefindings:

1) Eachof the 4 species were induced to flowerby cold treatment; at least 10 weeks wererequired for columbine (Figure 1), 12 forbasket-of-gold and lupine (Figure 2), and 16for Shasta daisy.

2) Flower-inducing treatments were not effective until after plants were mature, as shown inTable 1.

Thus, 2groups of species have been identified:

A. quick-maturing types which require only 3months of vegetative growth at 65° before coldstorage.

B. slow-maturing types which require 6monthsofvegetativegrowthat 65° before coldstorage.

Because of this required minimum size, onlycolumbine could be produced from transplantto finish in small volume cell packs (48 cells/11inch x 21 inch flat). The large size of themature plants necessary for flower induction ofbasket-of-gold, Shasta daisy, and lupinenecessitated the use of larger volume cells (18cells/11 inch x 21 inch flat), or 3 to 4 inch pots.

3) While seed catalog information was sufficient for germination of most species, theneed to scarify lupine seeds is not listed. A45-60 minute soak in concentrated sulfuric acidimproved germination in 4 days from 3%without scarification to 81% with scarification.

Table 1. Minimum Age (Size) for Cold Treatment of 4

Herbaceous Perennial Species.

Species

Columbine

Shasta Daisy

Basket-of-Gold

Lupine

Earliest Stage Plants Ready

for Flower-Inducing Treatments

Description Approximate Age (mo)

12-15 Leaves

Multiple Crowns

10 Crowns

4) Forcing cold-stored plants to visible flowerbuds before spring sales was achieved in arange of times. Time varied according towhether plants were grown under short day-lengths or long daylengths.

Forcing periods Cor A herbaceousperennial species when grown inlong clays or short days.

Approximate Forcing PeriodFor Visible Flower Buds

(weeks)Short Days Long HaysSpecies

Columbine

Shasta DaisyBasket-of-Gold

Lupine

4-7

Long daylengths during forcing hastenedflower bud development by 1-8 weeks compared to short days and may be used commercially for this purpose.

5) Long daylengths caused plants to elongate,especially columbine and basket-of-gold, so agrowth retardant might be needed. Forcolumbine, a B-Nine spray at 2000 ppm wasquite effective when applied when some newfoliage had developed after coldstorage.

CONCLUSION

Production of perennial bedding plants tomarket with spring annuals is feasible. Thetechnology differs by earlier sowing followedby a cold treatment. The date of sowing isaffected by the length of the juvenile period(Table 1), as well as the length of the inexpensive summer growing period. (Droppingtemperatures to 40°F in November saves fuelcompared to maintaining 65° through December). Thus basket-of-gold and lupine would besown in April, and columbine and Shasta daisyin July. By November, plants are mature andready to move to cold storage. Facilities mightconsist of coldframes, unheated greenhouses,or refrigerated storage. Time of raising the

'Russell Hybrid' lupine produced as a containerized bedding plant.

BPI News • August, 1982

temperature for forcing depends on marketdemand, but would usually begin in early Aprilfor columbine and Shasta daisy, late April forbasket-of-gold and lupine. Forcing temperatures may be adjusted to slow down or speedup bud development as needed.

Consumers need to be made aware that theseplants are spring and early summer floweringspecies, and should be encouraged to buy andplant them as soon after the frost-free date intheir area as possible.

When considering these results along withthose of Lopes and Weiler, and Kusey et al.,natural causes of flowering in the perennialgarden seem to be the following:

J. Amer. Soc. Hort. Sci. 102(4):388-390.5. Kusey, W.E. Jr., T.C. Weiler, P.A.

Hammer, B.K. Harbaugh, and G.A.Wilfret. 1981. Seasonal and chemical in

fluences on the flowering of Gypsophilapaniculata 'Bristol Fairy' selections. J.Amer. Soc. Hort. Sci. 106(1):84-88.

6. Seeley, J.G. and A.H.Weise. 1965. Photoperiodic response of garden and greenhouse chrysanthemums. Proc. Amer. Soc.Hort. Sci. 87:464-471.

7. Shedron, K.G. and T.C. Weiler. 1982.Regulation of growth and flowering inAquilegia x hybrida Sims. J. Amer. Soc.Hort. Sci. In press.

8. Shedron, K.G. and T.C. Weiler. 1982.

Table 3. Natural blooming season and cause of flowering for severalherbaceous perennial species.

Flowering Period Species

May Basket-of-Gold, Bleeding Heart

Causes of Flowering

Winter Cold

June-July Columbine, Lupine, Shasta Daisy Winter Cold

and Summer

(long) Daylengths

July-August Baby's Breath Summer (long)Daylengths

September Chrysanthemum Fall (short)

Daylengths

1.

LITERATURE CITED

Beam, J. 1980. Production of perennials.Ohio Florists' Assn. Bui. 605:8-10.

2. Cathey, H.M. 1970. Growing floweringperennials. Home and Garden Bui. 114,USDA,Washington, D.C. 32 pp.

3. Hebb, R.S. 1975. Low maintenance perennials. New York Times Book Co., NewYork. 220 pp.

4. Lopes, L.C. and T.C. Weiler. 1977. Lightand temperature effects on the growth andflowering oi Dicentra spectabilis (L.) Lem.

BPI News - August, 1982

'Fairyland' Columbine producedas a containerizedbedding plant.'McKana's Giant' Columbine

elongated more and requiredchemical growth retardant.

Regulation ofgrowth and flowering in Basket of Gold, Aurinia saxatilis (L.) Desv.HortScience. In press.

9. Shedron, K.G. and T.C. Weiler. 1982.Regulation of growth and flowering inChrysanthemum x superbum Bergmans.J. Amer. Soc. Hort. Sci. Inpress.

10. Shedron, K.G. and T.C. Weiler. 1982.Regulation of growth and flowering inLupinus 'Russell Hybrid.' HortScience. Inpress.

11. Walters, D. 1977. Personal communication. Walters Gardens, Zeeland, Mi.

PhotographicCrop Records

Terry HumfeldAg. Tech. Instit.Wooster, Oh.

Timing and scheduling play a very keyrole in the production of all greenhousecrops. The grower may use a variety oftechniques to finish a crop by a certaindate. These include pinching techniques,temperature control, and watering practices, just to name a few. However, eventhe best grower is at the mercy of MotherNature. Low light levels, cold or hottemperatures, or a rainy May weekendcan have drastic effects.

Just as Easter lilies are difficult to sell the

day after Easter, bedding plants willusually require the presence of a flower tobe sold. The young and inexperiencedgrower will usually feel uncertain abouthow well the crop has been timed untilseveral have been grown.

Potted plants and bedding plants usuallygo through a series of distinct changesduring the time they are in the greenhouse. Educators and university extension personnel will routinely make use ofcolor slides as part of their presentationson crop timing and culture. Growers mayalso find photographs of a prior crop atvarious stages of growth to be very helpful in determining how a current crop isprogressing.

Instant print cameras are now available atreasonable cost and will simplify thewhole process. However, for the photograph to be meaningful, the grower willhave to take a few notes and keep themwith the photographs. The following aresome items to consider:

• height and spread - you may want toput a well known item in the picture(coins, pencils, etc) to use as a point ofreference in judging size. Ideally, theplant should be placed in front of abackground that has been marked offin inches or centimeters.

• outside weather conditions - has the

weather been hot, humid, dark, cold,etc. since the last picture was taken?

• interior conditions - record average dayand night temperatures, use of C02.etc.

• Finishing Notes - Record the stage ofdevelopment at the time of marketing.This would also be the time to write

down any changes you would like tomake next year.

The grower will then have a complete