basil (o. basilicum)
DESCRIPTION
Some facts regarding Basil, French basil, or sweet basil (Ocimum basilicum L.), a tender annual is a popular herb known for its flavorful foliage.TRANSCRIPT
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Basil
R Dinesh Indian Institute of Spices Research
Calicut, Kerala, India 1.0 Introduction Basil, French basil, or sweet basil (Ocimum basilicum L.), a tender annual is a popular herb
known for its flavorful foliage. The term Basil is collectively used to describe plants of the genus
Ocimum, Family Lamiaceae (formerly Labiatae). The common names are Sweet basil, Common
Basil, French Basil, Basil and Bush Basil (Hortus Third, 1986; Simon et al., 1990a; Hornok,
1992).
Although several ornamental varieties are sold commercially, basil is primarily cultivated for its
aromatic leaves, which are used fresh or are dried for use as flavouring agent. Sweet basil is
reputed to be the sweetest in flavour among the basil species and is the darkest in colour. The
fresh or dried leaves add a distinctive flavor to many foods, such as Italian style tomato sauces,
pesto sauce and salad dressing. The essential oils and oleoresins are extracted from leaves and
flowers and used for flavoring in liqueurs and for fragrance in perfumes and soaps. During the
course of medicinal plant history basil has been both praised and excoriated. Early herbalists
asserted that basil damaged the internal organs, the eyes and caused insanity. Subsequent writers
argued that basil did none of these things, but was good both as a condiment and for a variety of
medicinal purposes (Low et al., 1994).
2.0 Composition and uses
As with many herb oils, the characteristics of basil oil changes between countries and plant parts
(De Masi 2006; Telci et al., 2006). This is most likely a result of different environmental
conditions and different cultivars. "True" sweet basil oil is a colourless or pale yellow liquid with
a light, fresh sweet-spicy sent and balsamic undertone (Lawless, 1992). Exotic basil oil which
comes from the plant commonly known as "bush basil", taxonomically classified as Ocimum
basilicum, is described as having a yellow or pale green colour, with a slightly course sweet
herbaceous odour, and a camphoraceous tinge (Lawless, 1992).
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The main oil constituents of "true" sweet basil are linalool (40-45%), methyl chavicol (23.8%),
and small amounts of eugenol, limonene and citronellol among others (Lawless, 1992). Bush
basil is mainly methyl chavicol (70-88%) with small amounts of linalool, cineole, camphor,
eugenol, limonene and citronellol (Lawless, 1992). However, many of these constituents are
variable depending on the country of origin and the plant history (Table 1).
Table 1. Chemotaxonomic classification of Ocimum basilicum based on the U.S.D.A. germplasm
collection (adapted from Simon et al., 1990a).
Plant number or Cultivar name
Predominant Constituents Country of Origin
175793 linalool Turkey 368699 linalool, 1,8-cineole Yugoslavia 358465 linalool, geraniol Yugoslavia 174285 linalool, methyl chavicol Turkey 190100 methyl chavicol, linalool Iran 253157 methyl chavicol, citral Iran 170579 methyl cinnamate, and Z
isomer Turkey
170579 methyl chavicol, methyl chavicol, linalool
Turkey
Purdue selection methyl eugenol Thailand
Twelve aroma constituents of basil were examined for their antioxidant activities using the
aldehyde/carboxylic acid assay. Eugenol, thymol, carvacrol, and 4-allylphenol showed stronger
antioxidant activities than did the other components tested in the assay. They all inhibited the
oxidation of hexanal by almost 100% for a period of 30 days at a concentration of 5 g/ml. Their
antioxidant activities were comparable to those of the known antioxidants, -tocopherol and
butylated hydroxy toluene (Lee et al 2005).
The value of its essential oil in the international market, however, depends on the percentage of
linalool. Studies on the morphological and agronomic characteristics (plant height, dry matter of
aerial parts, yield and essential oil content) of 55 O. basilicum, O. sanctum [O. tenuiflorum] and
O. gratissimum genotypes from the Ocimum Germplasm Bank of the Universidade Federal do
Sergipe, Brazil, indicated wide genetic variation among genotypes for all the morphological and
agronomic traits evaluated. The essential oil content and yield of genotypes ranged from 0.202 to
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2.536 ml/100 g and from 1.103 to 21.817, respectively (Blank et al., 2004).
Aroma compounds in the extracts of basil leaves (Ocimum basilicum L.) were identified by gas
chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The major aroma
constituents of basil were 3,7-dimethyl-1,6-octadien-3-ol (linalool; 3.94 mg/g), 1-methoxy-4-(2-
propenyl) benzene (estragole; 2.03 mg/g), methyl cinnamate (1.28 mg/g), 4-allyl-2-
methoxyphenol (eugenol; 0.896 mg/g), and 1,8-cineole (0.288 mg/g) (Lee et al 2005).
Linalool, methyl chavicol, eugenol, bergamotene, and methyl cinnamate were found to be the
dominant volatile components, the relative content of which was found to enable differentiating
between the basil cultivars examined. The relative content of some sesquiterpenes, hydrocarbons
benzenoid compounds, and monoterpene hydrocarbons was lower in dried and frozen leaves as
compared to fresh basil leaves (Klimnkov et al., 2008).
Oil Types
European type
Distilled from O. basilicum grown in Europe and America and commonly known as oil
of Sweet Basil. Its major constituent is methyl chavicol and linalool, but no camphor. It is
highly prized for its fine odour.
Reunion type
Distilled originally in Reunion Islands. The oil contains methyl chavicol and camphor but
no linalool.
It possesses a camphorraceous by-note and is considered inferior to the European oil.
Methyl cinnamate type
Distilled in Bulgaria, Sicily, Egypt, India and Haiti. It contains methyl chavicol, linolool
and substantial amount of methyl cinnamate but no camphor.
Eugenol type
Distilled in Java, Seychelles, Samoa and the Commonwealth of Independent States
(esrtwhile USSR). It contains eugenol as the main constituent.
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Sweet basil (Ocimum basilicum) has several culinary, ornamental, medicinal and aromatic uses
(Blank et al., 2004) and sold as a fresh herb and as a dried spice (Raimondi et al., 2006) It is a
source of essential oils and aroma compounds (Simon et al. 1984, 1990b), a culinary herb, and an
attractive, fragrant ornamental (Morales et al. 1993; Morales and Simon 1996). The seeds
contain edible oils and a drying oil similar to linseed (Angers et al. 1996). Extracts of the plant
are used in traditional medicines, and have been shown to contain biologically active constituents
that are insecticidal, nematicidal, fungistatic, or antimicrobial (Simon 1990; Albuquerque 1996).,
Besides being a culinary herb, basil is a well-known source of flavouring principles (Petropoulos
et al., 1995; Javanmardi et al., 2003; King and Duineveld, 2006) and therefore is recognized as
an important herb in cooking to flavour Italian, Mediterranean and Thai dishes and in tomato and
pesto sauces. Basil is also good with fish, poultry, pasta, rice, tomatoes, cheese and eggs. Dried
leaves and tender four-sided stems of this plant are used as a spice for flavouring and for the
recovery of essential oil. The flavour is warm, sweet and somewhat pungent and peculiar. The
odor of sweet basil is aromatic, fragrant and sweet. Basil is used as a condiment in a number of
countries, especially in southern European countries, U.S.A. and Australia (Simon et al., 1990a).
Essential oil and oleoresin are also extracted from the leaves and flowering tops by steam
distillation and used in place of the dried leaves for flavoring purposes (Simon, 1985).
Basil oil is also used to flavour dental and oral products, in fragrances and for traditional
medicines (Guenther, 1950; Simon et al., 1990a). The two minor components of the oil -
juvocimene I and II are reported to act as juvenile hormone analogs (Simon et al., 1990a). The
extracts from basil also possess excellent antioxidant properties (Javanmardi et al., 2003;
Hinneburg et al., 2006; Juntachote et al., 2006; Kivilompolo and Hytylinen, 2007) and is also a
potential source of anthocyanins (Simon et al., 1999).
A tea is made from the leaves (zcan et al., 2008) and used for nausea, gas pains and dysentery.
Basil's effectiveness as a carminative has been established, and research shows that extracts of
the plant inhibit organisms that can cause dysentery (Low et al., 1994). When used as a
companion plant, basil is reported to increase the growth of peppers and the growth and flavour
of tomatoes.
3.0 History and origin
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Basil is a member of the Lamiaceae (mint) family and is native to Asia and India where it is
considered sacred. It is indigenous to the lower hills of the Punjab and Himachal Pradesh and is
cultivated throughout India. Basil is now cultivated commercially in Europe, Africa, Asia and the
United States, but the main center of diversity appears to be Africa (Paton 1992).It is grown as
an ornamental plant and cultivated commercially for its green, aromatic leaves, which are used
fresh or dried as a flavoring or spice. In recent times Basil has become a popular condiment, and
is naturalised in many parts of the world expanding from its original Asian origin. In Australia
Basil is widely grown as a condiment, and has naturalised in Queensland (Low et al., 1994)
4.0 Botany
Basil is glabrous or glabrescent annual with leafy stems and thin, branching roots and reaches a
height of up to 60 cm at maturity. It is a summer annual from a tropical origin in the old world
(Hortus Third, 1986). Sweet basil leaves are yellow-green to dark green, depending on soil
fertility, and are about 3.75-5.0 cm long. Leaves are ovate to ovate elliptic, 7-13 cm long,
generally cuneate. When dried they turn brownish-green, whole and broken, brittle, curled or
folded together. The flower infloresence is a racemose, and the corolla is about 8 mm long, white
or purplish. The tiny seeds are dark brown. Sweet basil bears white flower spikes which bloom
from July to August.
The leaves have numerous dot-like oil glands in which the aromatic volatile oil of the herb is
contained. The herb bears clusters of small, white, two-lipped flowers in raceme fashion
Since the plant is very variable and its botanical nomenclature is complicated, several
designations have often been assigned to one or the same type. Polymorphism and cross-
pollination under cultivation have resulted in a number of sub-species, varieties and races
differing in height, growth habit, degree of heaviness and colour of stems, leaves and flowers.
Hence, some forms and types have been confused with other species.
5.0 Classification and varieties There are between 50 and 150 species of herbs and shrubs in the genus Ocimum, differing in
growth, habit, colour, and aromatic composition (Simon, 1989; Simon et al., 1990a), making the
botanical identification of Basil difficult (Hortus Third, 1986). They differ in growth habit,
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cohort and aromatic composition. Ornamental types of basil are commercially available and
include types with purple foliage (i.e. Dark Opal) or varying growth habits (i.e. bush basil).
Basil for the fresh market should have a sweet flavor and dark green foliage. Commercially,
there are three major types of basil having essential oil or dried leaves as their end product.
French basil, reputed to be sweetest in flavor and darkest in color, is the most valued. American
basil, noted for its rich color, sweet flavor, cleanliness, and uniformity of particle size, is
considered to be of very high quality. Egyptian basil also known as Reunion or African basil has
fragrance of camphor and different flavor and so is considerably less expensive.
While basil seed is plentiful, care must be observed in obtaining a type that has desirable
characteristics. Because several basil types may be mixed together either by a seed house or
processor to achieve a desired blend, any collected seeds that are later sown may vary in their
growth, development, and aromatic properties.
Many types of basil are available, depending on use. For fresh market production, basil with
good flavor and attractive, dark green or purple foliage is selected. Sweet basil (Ocimum
basilicum L.) is the culinary classic. Italian, Lettuce Leaf and Opal are popular sweet basil
varieties. Scented basils, such as Lemon, Licorice and Cinnamon basil, are used fresh or dried in
potpourri, jellies, honeys, vinegars and baked goods. For production of dried leaves or essential
oils, French, American or Egyptian basil may be grown. There are also several ornamental type
basils.
There are numerous varieties of O. basilicum of which, four are identified in India. They are var.
album Benth (Lettuce-leaf basil), var. purfrascens Benth (violet red basil), and var. thyrsiflorum
Benth (common white basil). Curly leafed basil is considered most suitable for cultivation; it is
grown in France and is reported to give good yields of high quality oil.
6.0 Genetics/ breeding/ micropropagation Basil seed is available around the world, but the identification and purity of this seed is
questionable. The U.S.D.A., germplasm repository has an extensive collection of Basil (Ocimum
basilicum) cultivars, many of which have been both taxonomically and chemotypically
classified. A number of different chemotypes have been identified and field tested under U.S.
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growing conditions (Simon and Reiss-Bubenheim, 1987).
An efficient protocol has been developed for rapid micropropagation of Ocimum basilicum.
Multiple shoots were induced by culturing shoot tip explants excised from mature plants on a
liquid Murashige and Skoog (MS) medium supplemented with 5100 M of thidiazuron (TDZ)
for different treatment duration (4, 8, 12 and 16 d). The optimal level of TDZ supplementation to
the culture medium was 50 M for 8 d induction period followed by subculturing in MS medium
devoid of TDZ as it produced maximum regeneration frequency (78 %), mean number of shoots
(11.6 1.16) and shoot length (4.8 0.43 cm) per explant. The regenerated shoots rooted best on
MS medium containing 1.0 M indole-3-butyric acid (IBA). The micropropagated shoots with
well developed roots were successfully established in pots containing garden soil and grown in
greenhouse with 95 % survival rate. The regenerated plants were morphologically uniform and
exhibited similar growth characteristics and vegetative morphology to the donor plants (Siddique
and Anis, 2007).
An efficient plant regeneration protocol has also been developed for basil (Phippen and Simon,
2000). Explants from 1 month old seedlings yielded the highest frequency of 85% regeneration
with an average of 5.1 shoots per explant. The regeneration protocol was performed on three
basil varieties (Sweet Dani; Methylcinnamate; Green Purple Ruffles). Callus and shoot induction
was initiated on MS basal medium supplemented with thidiazuron (16.8 M) for approximately
30 d. Shoot induction and development were achieved by refreshing the induction medium after
14 d. The most morphogenetically responsive explants were from the first fully expanded true
leaves of greenhouse-grown basil seedlings. All developing bud tissue demonstrated temporary
anthocyanin expression; however, anthocyanin expression in Green Purple Ruffles remained
stable until maturity. Developing shoots were rooted in the dark on media with thidiazuron
removed. Within 20 d, rooted plantlets were transferred and acclimatized under greenhouse
conditions where they developed normal morphological characteristics. This is the first report of
a successful in vitro regeneration system for basil through primary callus.
A scale-up micropropagation technique enhanced accumulation of rosamaric acid in sweet basil.
The nodal explants with lateral buds and leaf-derived suspension cultures were cultured in 5 l
airlift bioreactors for three weeks, thereby increasing the fresh wt of suspension cultures 2.5-fold.
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Rosmarinic acid accumulated at 29 g g1 dry wt in the suspension culture but, for
micropropagated plants, it reached 178 g g1 dry wt (Kintzios et al., 2004)
7.0 Soil and climate Basils are native to tropical climes and are considered annuals in our climate because they are
hardy to only 32F. They require a minimum of four hours of direct sun per day. They should be
planted in a soil that is rich, loamy, and well-drained with a pH of 5.5 to 6.5. The soil needs to be
kept moist to hasten germination and to ensure a uniform stand, when plants emerge within two
weeks. Basils should not be planted outdoors until the warmth of frost free mid May because
these tender plants react unfavorably to cool, damp weather (DeBaggio Herbs, 2007)
8.0 Cultivation 8.1 Land preparation The land is prepared to good tilth by ploughing, harrowing and levelling. 10 tonnes of well rotten
FYM, 100 kg DAP and 100 kg muriate of potash per hectare are applied as basal dose. A better
option is to plant basil seed and seedlings in beds following a good fallow, ripping, discing, and
tilling with a rotary hoe fitted with bed formers. Beds can be spaced 60-90 cm apart and two
staggered rows (20-30 cm between rows) sown on each bed. Beds wider than 50cm with more
than 2 rows of plants can tend to show reduced middle row growth, as a result of light
competition. Basil needs full sun to achieve high leaf production levels. If excess shading occurs
the plants will etiolate and produce little leaf. High light conditions maximise the oil yield.
8.2 Seeds/planting material Basil may be cultivated either as a field-grown crop or in a greenhouse. It can be propagated
using seeds, cuttings or transplants, seeding or transplanting to the field once seedlings are more
advanced. To ensure a good crop, high-quality seed is important and should be purchased from a
reputable source. Quality, trueness to type, high germination percentage, and reliability are more
important than price when considering the purchase of seed. The optimum storage temperature of
basil seed is 5C, however, the seed does lose viability quickly. The germination rate of basil
seed should be 80 - 95%, and seed should not be used if the germination rate is below 70%
(Simon, 1989).
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Basil seed is large and is germinates easily, hence field establishment by direct sowing in a
nursery is a good production option. About 125 g viable seeds are required for one hectare (1000
seed weigh a little over 1 g). The seed germination starts 3 days after sowing and is practically
over in about 10 days. The seedlings are ready for planting after 4 - 6 weeks of sowing.
However, Basil is a frost tender annual, and in areas where the frost free period is short,
establishment by seedlings is more viable.
The large seed of Basil makes seeding in individual cells with a vacuum seeder relatively simple.
For small scale operations a home made vacuum seeder is suitable. A plastic box the size of the
seeding tray can have a plastic fitting attached to fit a household vacuum cleaner, the opposite
side should be drilled with 0.5mm holes positioned to correspond with the centres of each cell.
When the vacuum cleaner is on seeds will be held against the holes until placed over the seedling
tray, and the vacuum cut. This method can allow a large number of trays to be seeded in a
relatively short time (RIRDC Research Paper Series No 97/18, 1997).
For the planting of large areas of Basil, the cost of buying prepared seedlings from an established
nursery would be more economical than trying to produce seedlings in an under-equipped home.
Basil is also relatively easy to grow from cuttings, however, cuttings would only be used for
selection and breeding trials to increase the population of a selected line. The ease of seed
germination, and the annual nature of basil plants, does not make clonal establishment a viable
option.
8.3 Planting Basil can be direct seeded or transplanted to the field in late spring after all danger of frost has
passed. The germination rate of the seed should be 80-95%, and seed should not be planted if the
germination percentage is less than 70%. If the soil is heavy, the seed should be covered with an
anticrustant. The soil should be kept moist to hasten germination and to ensure a more uniform
plant stand. The seed is relatively small, and a good friable, well-tilled and uniform seedbed is
required for optimum plant establishment. Seeds should be planted only 1/8 - 1/4 inch deep. For
direct seeding, seed is planted only 3 to 6 mm deep at a spacing of 2.5 mm apart (8 to 10 per
inch). Hornok and Lenches (1992) recommend sowing basil seed at a depth of 0.5 cm using
about 2-3 kg of seed per hectare. Plant emergence should occur between 8-14 days. To
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encourage lateral branching and growth, the tops of transplants can be trimmed prior to field
planting, when they are about 6 inches tall.
The seedlings are planted at a spacing of 60 cm between the rows and 40 cm between the plants
in April - May or August - September. The field is irrigated on alternate days until plants
establish, thereafter the crop is irrigated at 5 - 7 day intervals during non-rainy periods. However,
the plant spacing for Basil varies from country to country, usually depending on the type of
machinery used. A good spacing is to grow basil in rows spaced 60 to 90 cm apart, with plants
spaced every 15cm in the row. Beds can also be used with two to three rows per bed. Rows
should be 30cm apart and the plants spaced between 15 -30 cm in the row (Simon, 1989). It is
not advisable to plant more than three rows per bed as shading will reduce growth in the centre
rows.
Basil is easy to grow but is very susceptible to cold weather. For any grower who wants an early
crop, seedlings should be started indoors by sowing seeds in trays or flats. While in the
greenhouse, plants can be trimmed to encourage branching and then transplanted into the field
when they have reached 15 cm in height, in about four to six weeks. Plants should be spaced 15
to 30 cm apart in rows which are 0.5 to 1.0 m apart, depending on the nature of the inter-row
cultivation equipment. Double-row plantings on beds between 0.5 and 1.2 metre wide increase
yields and held to shade out weeds. Large producers plant 70,000 to 84,000 plants per hectare
(30,000 to 35,000 per acre).
While the optimum population density is dependent upon the end use, a higher density can be
grown if compatible farm equipment is available for mechanical cultivation and seeding. Rows
24 to 36 inches apart, with plants spaced every 6 inches in each row, are recommended Basil can
also be planted in a bed of 3 rows 12 inches apart with 12 inches between rows. The distance
between the beds, ranging from 24 to 36 inches, is dependent on available equipment. Large
variations in growth and yield may occur due to climate conditions, plant type, and cultural and
management practices.
Weed control is critical during the establishment of basil plants. If weeds are not well controlled
during the fallow and cultivation periods, high labour and / or chemical controls will be
necessary.
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8.4 Fertilizers
It is generally suggested that 110 to 135 kilograms each of N, P2O5 and K20 per hectare (100 to
120 pounds per acre) be broadcast and incorporated at the time of planting. If more than one
harvest is made, a side-dressing with 16 to 33 kilograms N per hectare shortly after the first or
second cutting is recommended.
Split application of N is also recommended by fertilizing thrice with 50 kg urea per hectare each
time. First dose is given during transplanting, the second and third after one and two months of
transplanting. In Zn deficient soils, 25 - 50 kg Zinc Sulphate per hectare is applied. However, the
rates of fertilizer application will depend upon the soil type and the previous crops and fertilizer
applications. Over fertilizing basil sacrifices flavour for growth.
U.S. recommendations are to apply an N:P:K fertilizer ratio 1:1:1 at a rate of 120 kg per ha, then
sidedress with 20-30kg N per ha after the first harvest. Increased nitrogen levels will improve the
leaf biomass and crop colour, however, Hornok (1983) showed that moderate levels of nitrogen
and high levels of P increased the essential oil content. The oil composition of basil can be
changed by the use of unbalanced nutrient additions. Basil plants displayed a significant decrease
in their main components (menthol and linalool) as nitrogen levels were increased (Hornok,
1983; Adler et al., 1989). However, an increase in potassium caused an increase of menthol and
linalool, while varying phosphorous levels had no effect (Hornok, 1983). This ability to change
the chemical composition of the oil by various nutrient combinations is important when
supplying companies who require specific oil chemistry. In a study on the effect of N
fertilization on the growth, yield and essential oil content of basil, it was found that N
fertilization up to 300 kg ha1 increased yield of above-ground and leaf fresh biomass, leaf
essential oil yield, but it did not affect leaf-to-stem ratio, plant height and the number of
branchings per plant. The increase in essential oil yield induced by N fertilization depended on
an increase in both leaf essential oil concentration and leaf biomass (Sifola and Barbieri, 2006)..
Mulching is recommended for basil production because it ensures moisture retention, prevents
weed growth and keeps the foliage clean from the soil. The most commonly used mulch is black
plastic, which encourages an early first harvest by warming the soil in the spring.
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8.5 Irrigation
Basil should be treated as a leafy vegetable when considering water requirements and cannot
tolerate drought stress. During seedling establishment beds should be always moist but not wet,
and during growth the plants like to be in moist, well drained soil. Water needs to be applied
regularly throughout the growing season to maintain constant growth. Although basil may be
irrigated with a simple overhead sprinkler system, a regular and even supply of moisture via drip
irrigation is best. Plants grown with drip irrigation are less likely to develop foliar diseases than
sprinkle-irrigated plants because the foliage stays drier. Research has shown that growing basil
with drip irrigation and black plastic mulch results in high yields of high-quality, clean leaves.
8.6 Inter-cultivation
Weed control is critical because competition with weeds decreases the quality of basil leaves. To
keep weed populations low, high plant populations, shallow cultivation, or mulching should be
used. The field is kept free of weeds during the initial stages of crop growth and after first
harvest by manual weeding. To keep weed populations low, use high plant populations, shallow
cultivation, or mulch. Mulch, plastic or organic, also helps retain moisture in the soil and
prevents soil from being splashed onto the foliage.
Presently, high plant populations of basil coupled with mechanical cultivation are recommended.
Commercially labeled herbicides for weed control in basil fields are not available. The presence
of weeds in fresh or dried basil leaves decreases the quality of the finished product.
Mulching is a good method of controlling weeds, and basil plants do well under mulch,
responding to both organic and inorganic forms. Plastic mulch has been shown to increase the
production of basil (Ricotta and Masiunas, 1983; Davis, 1994). However, the high humidity also
increased disease incidence (Davis, 1994). Davis (1994) also tested a number of other mulchs
with mixed success; however, if mulch is used the basil plants are normally established as
seedlings, and this plus the mulch greatly increase the cost of production.
8.7 Harvest
Leaf cuttings of basil may be harvested from one to five times per season, depending on the area
involved and the length of the growing season. For small-scale production of fresh-market basil,
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the terminal whorls of leaves are cut from the stems. The basil should be refrigerated as soon as
possible after cutting, preferably in the field.
Harvesting of basil should occur in the morning after the dew has left the plants but before the
heat of the day. If it is necessary to wash the basil after harvest, a water temperature of 13C
(55F) would be preferred and the material needs to be dried completely.
A sickle-bar mower with adjustable cutting height is commonly used for harvesting large
plantings for dried basil production. Foliage must be harvested before the plants bloom. Basil
plants will seed and stop producing leaves if the flower spikes are not removed as they appear.
Leaf yields can range from 2.5 to 7.5 tonnes per hectare (one to three tons per acre) of dried
material or 15 to 25 tonnes per hectare (six to ten tons per acre) of fresh material in California.
The plant part harvested depends upon the projected use. Where basil is grown for its dried
leaves and the extraction of essential or volatile oil, it is cut just prior to the appearance of
flowers. In the Mediterranean area and in other countries with similar climates, basil is grown as
a short-lived perennial, and 3-5 cuttings or harvests per year are achieved. In the more temperate
zones basil may be cut only 1-3 times. The first harvest in this case is very low, and the second
occurs just prior to open bloom. Generally, basil is harvested for its leaves, sold fresh or dried.
The foliage should be harvested, but only above the bottom two to four sets of true leaves.
A sickle bar gerry mower with an adjustable cutting height can be employed to cut the herb.
Leaves can be harvested when needed. The foliage should be cut at least 4-6 inches above the
ground to allow for regrowth and a subsequent crop. To ensure a continuous supply of leaves, the
field harvests and/or planting dates can be staggered accordingly.
- Leaf yields range from 1 to 3 tons per acre dried or 6 to 10 tons per acre fresh. Foliage may be
harvested whenever four sets of true leaves can be left after cutting to initiate growth, but when
harvesting for fresh or dried leaves, always cut prior to bloom. Presence of blossoms in the
harvested foliage reduces the quality, and consequently price, of the fresh and dried product.
Frequent trimming helps keep plants bushy. For small-scale production of fresh-market basil, the
terminal 2- to 3-inch long whorls of leaves may be cut or pinched off once or twice a week. This
provides a high quality product with little stem tissue present. Basil can also be cut and bunched
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like fresh parsley. A sickle bar type mower with adjustable cutting height is commonly used for
harvesting large plantings for dried production.
8.7.1 Harvesting for oil
The production of Basil oil is a broad acre enterprise. The oil yield varies between cultivars and
countries, and is highest in flowering plants (Prakash, 1990). Besides, the oil yield also varies
with the method of harvest (Kothari et al., 2004).
Kothari S.K., Bhattacharya A.K., Ramesh S (2004) Essential oil yield and quality of methyl eugenol rich Ocimum tenuiflorum L.f. (syn. O. sanctum L.) grown in south India as influenced by method of harvest Journal of Chromatography A, 1054:67-72.
The timing of harvest is determined by the composition and quantity of oil in the plant. The oil
yield and oil components will change during the year, but when the oil yield and desired oil
components are at their maximum, harvesting should commence. However, it is not always
advantageous to harvest when the oil concentration is at its maximum. It has often considered
that basil should be harvested at the onset of flowering (Basker and Putievsky, 1978; Hornok and
Lenches, 1992), as this is when the essential oil content in the plant approaches its highest.
However, if the plants are harvested prior to flowering, a greater number of harvests are possible
during the season, and the overall yield of leaf and oil is higher (Basker and Putievsky, 1978).
Hence, the best time to harvest Basil is during flowering (full bloom). On average the oil yield is
around 0.4% (Prakash, 1990). A Basil plot in with irrigation could be harvested two to four times
a year. The actual process of harvesting can utilize a standard forage harvester which will cut the
stems and deposit the cut material into a trailing distillation bin. This reduces the need for double
handling of the material prior to distilling. It is not necessary to de-stem or chop the material as
this may cause oil loss and increase the cost of processing.
8.7.2 Harvesting for dried leaf
When harvesting for dried product more care is required than when harvesting for oil, and
mechanical methods employing a cutter bar set in front of a conveyer belt are often used. The cut
material falls on the belt and is lifted up to collection bins, thus reducing bruising; a 10 to 12 cm
stubble is left providing a number of growing points for regrowth. Another method is to mow the
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Basil, allow it to partially dry, then windrow and pick up with conventional hay making
machinery (Hornok, 1992).
Following harvesting, the plant material may be washed to reduce soil and dust impurities, as
these will reduce the quality of the final product. If plants are grown on mulched beds the need to
wash the product is reduced. A blanching in boiling water is often combined with the washing
prior to drying to help maintain the dry colour (Rocha et al., 1993).
8.7.3 Harvesting for the fresh market Hand harvesting is the best method to collect plant material for the fresh market, as only top
quality leaves should be collected. The plants should be cut with a sharp knife or clippers, and
bunched. The bunches can be fastened with a rubber band and placed in cool boxes to start
removing field heat. A hand held hedge trimmer powered by a small petrol engine can be used,
reducing harvest time. Some form of sorting and classing is required after this form of cutting.
9.0 Pests and diseases Basil plants are susceptible to a number of fungal diseases which usually occur in wet humid
conditions (Simon, 1989). Davis (1994) describes how different mulches that maintained good
soil moisture cause significant plant losses, as a result of soft rot (Erwinia spp.). During
abnormally wet summers or wet weeks following irrigation, monitoring for disease outbreaks
would be necessary. Root and leaf soft rot are the main fungal disease, including Fusarium wilt
and the use of raised beds on free draining soil is the best control.
Though there are several insects and diseases that may infest the plant, but there are no pesticides
currently available for use on basil. Plants should therefore be monitored continually for the
presence of insects and diseases and preventive methods of using ridged beds and not irrigating
if there is a chance of rain are be the best production methods.
Therefore, prevention of disease through good cultural practices is the most effective means for
healthy crop production. To help prevent foliar fungal diseases, keep foliage as dry as possible
by watering early in the day so foliage dries quickly, or by using drip irrigation. To reduce soil
borne diseases, rotate herbs to different parts of the field each year and remove and destroy all
plant debris after final harvest.
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9.1 Diseases
A devastating basil wilt disease caused by a soilborne pathogenic fungus, Fusarium oxysporum f.
sp. basilicum (Elmer, 2001), was first discovered in the U.S. in 1991 and identified in N.C. in
1992. Plants infected with this disease usually grow normally until they are six to twelve inches
tall, then they become stunted and suddenly wilt. Initial symptoms usually include brown streaks
on the stems, discoloration of the internal stem tissue, and sudden leaf drop. Interestingly, only
sweet basil is affected. Some of the specialty basils, such as lemon basil and purple basil, show
some resistance to the disease.
The disease is introduced into fields, hydroponic systems, and greenhouse culture primarily
through contaminated seed. Growers should only buy basil seed that has been tested for the
fusarium wilt fungus. Currently, these tests involve growing out a large number of seed and
looking for disease symptoms. This does not guarantee that the seed will be free of infection, but
it greatly reduces the risk. If it is not possible to obtain tested seed, the seed should be soaked in
cold water for four hours followed by a heat treatment of 20 minutes in 133-136 degree F water.
Seed germination rates will probably be reduced by the hot water treatment, so a germination test
should be conducted on a small lot of the treated seed to determine how much seeding rates need
to be adjusted. Also, the hot water treatment causes a sticky layer to develop on the outer surface
of seed making it difficult to handle.
Once a field has become infested with the fusarium wilt pathogen, infective propagules may
persist in the soil for 8-12 years. During that time, growers should avoid growing sweet basil or
members of the mint family. Mints will not exhibit symptoms of the disease but may carry over
the inoculum from year to year. There are currently no products registered to help control this
disease. However, steaming with a soil-steaming machine and exothermic reaction by
incorporation into the soil of potassium hydroxide (KOH), a substance that causes an exothermic
reaction with water have been found effective against Fusarium oxysporum f.sp. basilici and
Sclerotinia minor on basil (Luvisi et al. 2006). The results show that steam combined with
exothermic reaction reduce the incidence of Fusarium wilt (77-96%) better than steam only (70-
89%). The control of Sclerotinia minor was better with potassium hydroxide (94-92%) than with
steam only (83-87%). Leaf spot disease probably caused by Cercospora guatemalensis Mueller
et Chupp has been observed in Chiba Prefecture (Japan) (Nishikawa et al. 2002).
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9. 2 Insect pests
Javelin (Bacillus thuringiensis) is the only insecticide registered for use on basil in North
Carolina. It is a biological control that kills a variety of caterpillars. If other insect problems
become serious, other organic methods may be tried. Reflective mulches, beneficial insects,
insecticidal soaps, traps and hand-picking may give some level of control.
10. Post harvest technology and value addition
Only the highest quality basil with the best colour and aroma should be used for fresh-market
sales. Basil once harvested should be stored at 4.5 to 7C (40 to 45F); lower temperatures may
cause discolouration and deterioration. Dried Basil should have a bright green colour, hence it
should be dried quickly in order to inactivate the enzyme chlorophyllase which breaks down
chlorophyll turning the leaf yellow-brown. Heat can destroy this enzyme quickly. However
temperatures in excess of 40C will remove the volatile oils (Deans et al., 1992) reducing
flavour. The moisture content should be reduced to less than 13%. Following drying the product
should be packaged and sent to market without delay as the loss of volatile oil is continuous.
Current specifications for the importing of spices into the U.S.A. do not include Basil, either
whole or ground.
A good commercial sample of sweet basil should contain a minimum of 0.4% volatile oil, a
maximum total ash content of 15%, maximum acid insoluble ash of 1.0%, maximum moisture of
8% and total ether extractives, a minimum of 4% on moisture free basis.
Before drying, basil stalks should be cut 15 cm above the ground and the foliage stripped from
the stems. Drying needs to occur on a screen in a warm, dark, well-ventilated place. Dried leaves
should be stored in the dark in airtight containers.
Leaves should first be washed and cleaned, with weeds and extraneous materials removed. The
quality of basil is determined by color and aroma retention. For the fresh market, only the highest
quality plant material should be sold. Prior to milling or distillation, the leaves and/or flowering
tops should be dried at low' temperatures (below 40 C) to retain maximum color.
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For fresh market sales, after harvest, wash and dry leaves and remove all weeds and flowers.
Only the highest quality basil with the best color and aroma should be used. Wholesale packs
may be prepared by filling perforated plastic bags with one pound of loose leaves. For retail
sales, small, uniform bunches of leaves may be tied and packaged. Keep all basil refrigerated
until sold. The optimum storage temperature is 40 to 450 F. Lower temperatures may cause
discoloration.
For a dried finished product, wash leaves, spread on screens, and sort out weeds and blossoms.
To retain maximum color, circulate warm air (less than 130 F) around the leaves until dry. Sun-
dried leaves tend to be brownish. Store in air-tight containers in the dark. For essential oil
production, cut basil should be field dried for 1-3 days prior to collecting and distillling.
11. Economics and marketing
Markets for the dried product need to be established before production begins as with any
agricultural product. While basil consumption in the US has increased eight-fold since 1960, the
market for herbs fluctuates greatly from year to year.
When deciding which varieties to grow, those which were in demand the previous year need to
be identified. Prices for herb products often vary from year to year, depending on supply and
demand for the product. In general, prices for culinary herbs in the US are more stable than those
for other herb products.
For small producers, fresh-market sales can be made to local restaurants, health food stores,
organic markets and gourmet groceries. Small-scale herb growers may also market value-added
products such as pesto, basil vinegar, and fancy-packed dried basil for sale in specialty shops.
Greenhouse herb plants can also be sold as herb bedding plants for transplanting to gardens.
http://www.newcrops.uq.edu.au/newslett/ncnl6154.htm Another development in herb production is fresh pot herbs. These are herbs produced in pots and
sold cheaply at supermarkets for use in kitchens. The herbs will provide a small volume of fresh
material to households while being an attractive ornamental plant. An economic plan of this form
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of production based in Southern Queensland showed Basil plants could be ready for sale every 6
weeks in summer and 8 weeks in winter. The return on capital invested was estimated at 58.65%
when a range of herbs were produced in this way (Avard et al., 1982). However, basil will not
withstand temperature below 5C so sales during the winter months would be limited.
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3.0 History and origin8.7.2 Harvesting for dried leaf8.7.3 Harvesting for the fresh marketLuvisi A, Materazzi A, Triolo E (2006) Steam and exothermic reactions as alternative techniques to control soil-borne diseases in basil Agron. Sustain. Dev. 26: 201-207.zcan M. M, Ahmet nver A, Uar T, Arslan D (2008) Mineral content of some herbs and herbal teas by infusion and decoction, Food Chemistry, 106: 1120-1127Raimondi, G., Orsini, F., Maggio, A., De Pascale, S., Barbieri, G. (2006) Yield and quality of hydroponically grown sweet basil cultivars. ISHS Acta Horticulturae 723 I International Symposium on the Labiatae: Advances in Production, Biotechnology and...