Basics of growing basil

Basil is native of tropical Asia, where for centuries, especially in India, it has been highly esteemed as a condiment. The early Greek and Roman writers were well-acquainted basil.

England used basil as early as 1538 and by 1586 it was a well-known herb. The Americans started using it about 100 years ago. It is mainly used for flavouring culinary concoctions. In Australia, it is also more or less grown, and in countries where French commerce or other interests have penetrated, it is well known.

There are several related species which attracted much attention in America. Europe or the East never caught on until much later. The most important of is dwarf or bush basil (O. minimum, Linn.), a small Chilian species also reported from Cochin China. It was introduced into cultivation in Europe in 1573. On account of its compact form, it is popular in gardens as an edging as well as a culinary herb, for more than a century it has been grown in America. Sacred basil (O. sanctum), an oriental species, is cultivated near temples in India and its fragrant oil extracted for religious uses. Initially, the common species was considered sacred by the Brahmins who used it to honour of Vishnu and funeral rites. An African species, O. fruticosum, is highly valued for its oils used in perfume.

So basil has a very wide use from adding aroma and flavour to food such as tomato pastes, ketchup and soups¹, medicinal, seasoning, decorative and in religious rituals. This makes growing and marketing basil, and similar herbs, much easier for the grower. Wide use and application ensure a strong market over the long term.

The oil in basil is claimed to alleviate headaches, the common cold, coughs, warts, worms, fever, malaria, infections and skin disorders². More serious application is to help with mental fatigue, migraine, depression³, blood glucose control and diabetics⁴. The anti-bacterial properties of basil are well known [/efn_note]Sakkas, Hercules & Papadopoulou, Chrissanthy. (2010). Antibacterial activity of Basil oil, Origanum oil, Thyme oil, Chamomile oil and Tea Tree oil. Hellenic Iatrica. 76. 28-36.[/efn_note]. Unfortunately, the composition of the essential oil harvested from basil is influenced heavily by climate and growth conditions. Commercial pharmaceutical application is difficult as consistency is essential.

The basil plant

From the small, fibrous roots the square stems stand erect about 1 foot tall. Basil is leafy with numerous branches. The leaves are green, except as noted below, ovate, pointed, opposite, somewhat toothed, rather succulent and highly fragrant. The little white flowers which appear in midsummer are racemed in leafy whorls, followed by small black fruits, popularly called seeds. These, like flaxseed, emit a mucilaginous substance when soaked in water. About 23,000 weigh 30g, and 250g fill 500ml. Their vitality lasts about eight years. Basil seeds are very small and light which makes planting accuracy difficult.

Like most of the other culinary herbs, basil has varied little in several centuries but there are some distinct differences in commercial varieties based on leaf size, shape, smell or odour and colour.

• Common basil with dark green spiky leaves
• Curly leaved basil with short spikes of flowers
• Narrow leaved basil which smells like Fennel, citron or tarragon.
• Variegated basil with various coloured leaves on one plant.

There are many modern commercially grown varieties available, each suitable for a specific market segment.

• Sweet and bush basils
• Purple foliage basils
• Lemon basils
• Others specialist types such as Cinnamon basil, Spicy Bush, Camphor, Anise, Licorice

The dwarf species, also referred to as studded, is more compact, branching and dainty than the common species. It has three varieties; one with deep violet foliage and stems and lilac white flowers, and two with green leaves, one very dense and compact.

In some climates downy mildew resistance is more important than the type of basil plant. So in those climates there is little choice. Read more about the development of these DMR varieties at Vegetable Growers News.

Growing basil commercially

Basil is a summer crop. The leaves are damaged by frost, so it must be grown in frost-free regions. It will grow successfully between 10-27 degrees Celcius but expect lower oil production or taste at lower temperatures. The leaves are soft and wilt quickly, so well drained moist soil is essential. In southern hemisphere lands daily drip irrigation is essential to prevent wilting and loss of yields. A plant that wilts is under stress and is susceptible to fungi and bacterial attack. Basil is not that sensitive to soil pH. It grows well from 4.5 to 8.4 pH values.

Basil is propagated by seeds and germination rate is typically above 80%. Because the seeds are very small, they are best sown in flats or seed trays under glass or shade cloth, covered lightly with finely sifted soil and moistened by standing in a shallow pan of water until the surface shows a wet spot. When the seedlings are about 25mm tall, the seedlings must be thinned out 50mm apart. When 75mm tall they will be large enough for transplanting, where they should be set in 300mm rows, 400mm to 500mm apart in the row.

For the best results obtain seedlings from a professional seedling grower as close to your farm as possible. They will know which varieties are suitable in your climate, based on experience.

If you don’t want to use a seedling grower you can make your own seedlings. A popular and very affordable method is using a seedbed. Sow the seed as early in the spring as possible without taking too much risk of frost. Basil is temperature-sensitive, so it grows well in moderate tropic temperatures. The ideal time to plant basil is in spring. A protected environment extends the planting time and heated greenhouses allow planting throughout the year. The seed germinates in 7-10 days in seed trays and some varieties within 5 days. Seeds sown in soil seedbeds take 8-14 days to germinate.

Start harvesting the basil leaves just before flowering. There is no advantage in leaving the plant after flowering as all resources are channelled to the reproductive organs. If the basil is harvested for oil production, the plant must be harvested in full bloom for maximum oil yields. To ensure a continuous supply of fresh leaves, the field harvest and planting dates are normally staggered. Roughly 50-65 days after transplanting, depending on the weather. In colder weather or south-facing lands, the first harvest might be up to 85 days. Some bush varieties mature in 40 days. Cut the plant so that 100-150mm of the stem is left. The stumps should develop a second and even a third crop if care is the land is kept clean of weeds. Apply top dressing to initiate strong growth for the next harvest. Growing basil seed some of the best plants should be left uncut. The seed should ripen by mid-autumn.

Basil reacts well to fertilizer. Initial application two weeks before planing of 200-350 kg N/ha. A second and third top dressing of 50-75 kg N/ha should be adequate for most soils ⁵. In very sandy soils apply three top dressings without increasing total amount of N. In warmer climates, and where the grown season of basil can be extended, N top-up rates up to 100-120 kg N/ha is not uncommon after the leaves are harvested.

Just be careful with nitrogen fertilizer, too much will darken the leaves reducing their marketing value. The plants will also wilt quicker and be more susceptible to insect damage and disease.

High concentrations of ammonia in the soil due to mineralization of organic material and fertilizers may cause the cotyledons to become chlorotic and necrotic. This effect is also called the nitrogen negative period and occurs approximately 2 weeks after organic material is worked into the soil. Subsequently, fungal diseases such as botrytis occur ⁶. At the end the best basil was produced with ammonium nitrate fertilizer.

Basil reacts much better to organic fertilizer than to conventional chemical fertilizers ⁷. This is good news for basil growers since organic material will improve the quality of the soil and does not pollute the underground water supply and rivers. Basil, just like spinach are grown for their leaf material which responds well to nitrogen fertilizer. The opposite is true for fruit crops, too much nitrogen fertilizer will reduce fruit yield and fruit quality and number of fruit produced.

Target markets for basil

Producing a crop without understanding your market is looking for trouble right from the start. Basil, like most herbs, are condiments. They are added to dishes for extra taste and appearance. Herbs are not stable foods. They are important supplements and contain very important nutrients that are essential for a vegan diet.

Basil is one of the most popular herbs in the French cuisine. It is especially relished in mock turtle soup, which, when correctly made, derives its peculiar taste chiefly from the clove-like flavour of basil. In other highly seasoned dishes, such as stews and dressings, basil is also highly prized. It is less used in salads. A golden yellow essential oil, which reddens with age, is extracted from the leaves for uses in perfumery more than in the kitchen.

The original and famous Fetter Lane sausages, formerly popular with Cockney epicures, owed their reputation mainly to basil. During the reigns of Queen Mary and Queen Elizabeth farmers grew basil in pots and presented them with compliments to their landladies when these paid their visit.

The main oils in basin are inalol, estragole and eugenol and are highly sensitive to environmental growth factors ⁸.

Basil is one of the easiest herbs to grow in NFT hydroponic systems.  Although bag systems are cheaper, basil can be grown at higher densities in NFT hydroponic systems with greater yields.  Learn all about hydroponic NFT and bag culture systems here.

1. Lupton, D., Mumtaz Khan, M., Al-Yahyai, R.A., Asif Hani, M., et al., 2016. Basil. In:Ambrose, D.C.P. (Ed.), Leafy Medicinal Herbs: Botany, Chemistry, Postharvest Technology and Uses. CAB International, pp. 21–47.
2. Twilley, D., Rademan, S., Lall, N., 2018. Medical Plants for Holistic Health and Well-being. Chapter 2 – Are Medicinal Plants Effective for Skin Cancer? Academic Press, pp. 13–75.
3. Singh, V., Kahol, A., Singh, I.P., Saraf, I., Shri, R., 2016. Evaluation of anti-amnesic effect of extracts of selected Ocimum species using in-vitro and in-vivo models. J. Ethnopharmacol. 193, 490–499. https://doi.org/10.1016/j.indcrop.2018.03.048.
4. Akbari, G.A., Soltani, E., Binesh, S., Amini, F., 2018. Cold tolerance, productivity and phytochemical diversity in sweet basil (Ocimum basilicum L.) accessions. Ind. Crops Prod. 124, 677–684. https://doi.org/10.1016/j.indcrop.2018.08.048.
5. Rangappa, M. & Bhardwaj, Harbans. (1998). Nitrogen Fertilization of Basil. HortScience. 33. 481a-481.
6. Frerichs, C., Daum, D. & Koch, R. 2019. Acta Horticulturae: 1242 pp29. Influence of nitrogen form and concentration on yield and quality of pot grown basil
7. Elziat, Rasha & Swaefy, Hend & Esmail, S. (2020). The Response of Red Rubin Basil Plant to Organic Fertilizer and Humic Acid versus Chemical Fertilizers.
8. Nykänen, Irma. (1989). The effect of cultivation conditions on the composition of basil oil. Flavour and Fragrance Journal – FLAVOUR FRAG J. 4. 125-128.