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Advice on Publications Available.The following article by Bethany Davidson and Iris Johnson featured in the Winter 1996 issue of BioOptions, Newsletter of the Center for Alternative Plant and Animal Products, University of Minnesota. It is reprinted here with the kind permission of the authors.
B.A. DavidsonThere are more than fifty species of basil (Ocimum spp.). They differ in growth habit, cohort and aromatic composition. Basil is a member of the Lamiaceae (mint) family and is native to Asia and India where it is considered sacred. Basil is cultivated commercially in Europe, Africa, Asia and the United States, where it is mostly grown in California.
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 a flavouring. Sweet basil (Ocimum basilicum L.), is reputed to be the sweetest in flavour among the basil species and is the darkest in colour. It is the basil species most commonly cultivated for the culinary market.
Basil has leafy stems and thin, branching roots and reaches a height of up to 60 centimetres at maturity. Sweet basil leaves are yellow-green to dark green, depending on soil fertility, and are about 5 centimetres long. The tiny seeds are dark brown. Sweet basil bears white flower spikes which bloom from July to August in the US.
The use of culinary herbs has increased over the past few years. Fresh or dried basil is used 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.
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 flavouring purposes (as described in Simon, J.E. (1985) Sweet Basil: A Production Guide. Cooperative extension Service, Purdue university. Bulletin HO-189).
When used as a companion plant, basil is reported to increase the growth of peppers and the growth and flavour of tomatoes. Traditionally, basil was used medicinally for digestive problems.
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.
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 centimetres in height, in about four to six weeks. Plants should be spaced 15 to 30 centimetres apart in rows which are 0.5 to a metre 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).
For direct seeding, seed is planted only 3 to 6 millimetres deep at a spacing of 2.5 millimetres apart (8 to 10 per inch). The soil should be a well-drained light sand to silt loam soil, 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.
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.
Basil cannot tolerate drought stress. 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, 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.
The rates of fertiliser application will depend upon the soil type and the previous crops and fertiliser applications. Over fertilising basil sacrifices flavour for growth.
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.
Pest control in herb production, both greenhouse and field production, is often hampered by a lack of pest control products. There are several diseases that may infest basil plants, including Fusarium wilt. Plants should be carefully monitored for the presence of insects and diseases.
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.
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, 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 13°C (55°F) 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.
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 7°C (40 to 45°F); lower temperatures may cause discolouration and deterioration.
Before drying, basil stalks should be cut 15 centimetres 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.
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.
On a commercial scale in California, medicinal herbs, dried bulk herbs, herbs for teas, and herbs for potpourri and spice mixtures are usually field grown.
Further reading
Davis, J.M. (1992) Basil Production Guide. Cooperative Extension Service, North Carolina State university. Bulletin AG-477
Witt, M.L. and S.S. Bale Herb Gardening in Kentucky II: Annual and Biennial Herbs. Cooperative Extension Service, University of Kentucky. Bulletin HO-49.
For further information
Appropriate Technology Transfer for Rural Areas (ATTRA)Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
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