Basil

Latin Name

• Ocimum basilicum L. Family: Labiatae (Lamiaceae)

Common Names

• Sweet basil
• St. Joseph Wort
• Common basil

In Saskatchewan, basil is a leafy, edible and fragrant herb that is grown outdoors in the summer and by greenhouse operators and home gardeners year round.

Basil is thought to have originated in India, Africa and Persia. There are many varieties of basil including both annuals and perennials. Breeding efforts have introduced hybrid varieties of basil that are suitable for various purposes. Although more than 50 different varieties of basil are known, fewer varieties are recommended for Saskatchewan (Table 1). The flower colour, growth habit, leaf colour, height and taste vary depending on variety. Basil plants typically grow between 60 and 90 cm in height.

Basil leaves can be processed into sauces like pesto, or be sold dried, frozen or fresh. Essential oils extracted from the leaves using steam distillation techniques are used to add flavour or odour to foods, toothpaste, medicine and fragrances.

Different types of basil produce different volatile oils, each with a characteristic flavour and odour: i.e. methyl chavicol (anise), methyl cinnamate (cinnamon), eugenol (clove), citral (lemon), geraniol (rose), linalool (lilac/orange blossom), thymol (thyme) and camphor.

Uses of Basil and Beneficial Claims

Basil is most often utilized as a fresh ingredient to add flavour to various foods. For example, it is often added to soups or pasta dishes. Basil is also used for its aromatic characteristic as an additive to soaps, toothpaste and mouthwash. Basil is also an additive for medical preparations and insect repellents.

Proponents of basil have made various beneficial medicinal claims, including treatment for upset stomach, migraines, insect bites, colds and flu. Manufacturing, packaging, labelling and importation of natural health products must comply with the Natural Health Products Regulations currently administered by the Canadian Department of Justice (see Information Sources).

Planting

Basil is a warm season crop – it is both frost sensitive and prone to chilling damage by cool temperatures. Transplanting basil outdoors after starting in a greenhouse is recommended. At optimum temperatures (21 C) in a greenhouse, basil seed germinates within six days after seeding and it takes six to eight weeks to produce basil transplants ready for the field. The seedlings should only be transplanted once all risk of frost has passed.

Sandy soils are preferred for basil production as they warm quickly in the spring and provide good drainage. Soils containing too much nitrogen can be detrimental to the quality of the oils produced in basil; moderate nitrogen fertility levels are recommended. The recommended fertilizer ratio is 1:2:1 Nitrogen: Phosphorus: Potassium (N: P: K). Composted animal manure is an excellent nutrient source for basil production.

Agronomic requirements for growing basil in Saskatchewan are still being researched. Current recommendations are to plant basil in rows spaced 60 cm apart with 30 cm between plants. Irrigation is best applied in six day intervals. Be careful not to over-water as excessive moisture may cause leaf spotting, reducing the value of basil sold in the fresh ingredient market.

By mid-season, basil grown outdoors begins to flower and then set seed, which diverts energy away from leaf production. Leaf yields can be increased by removing the flowers as they form.

Basil plants are susceptible to fall frosts; therefore, field harvest should be completed in a timely manner.

Greenhouse production extends the production season for basil as plants may continue to produce leaves suitable for harvesting year-round as long as flower buds are removed and plant health is maintained.

Weed Control

Basil is sensitive to weed competition as it is a small, slow growing crop. There are no herbicides registered for use in basil in Canada. Weed control options include:

• Selecting weed-free fields;
• Shallow inter-row tillage;
• Hand-picking weeds; and
• Growing the crop on plastic or mulches.

Disease Control

Basil is susceptible to fusarium wilt caused by Fusarium oxysporum f. sp. basilicum, an organism that infects the roots and vascular tissues of the plant. As the name implies, fusarium wilt causes the basil plants to turn yellow, wilt and die. Other diseases include damping-off, root rot, botrytis, downy mildew, powdery mildew and alternaria leaf spot. There are no fungicides registered for use on basil in Canada.

The best disease management is prevention. Reduce favourable conditions for disease organisms to infect your basil crop by:

Field production:

• Planting disease free seed;
• Selecting well drained sandy fields;
• Maintaining crop rotations; and
• Irrigating crops early in the day to allow for quick drying of the foliage.

Greenhouse production:

• Planting disease free seed;
• Selecting quality potting mix;
• Providing adequate air movement; and
• Using drip irrigation.

Harvesting

Whether growing in a greenhouse or outdoors, timing of harvest is critical to derive the best taste and quality. For fresh use, leaves should be picked prior to bloom. Remove flower heads as they form or else the leaves become tough and strongly flavoured. Pick basil in the morning after the dew has dried but before the sun's heat dissipates the essential oils that give it its intense flavor.

Extra care is required when harvesting basil as the leaves are easily damaged. It is best to pinch the stem off the plant, above a set of leaves, and then snip off the leaves. This technique encourages the two auxiliary buds below the cut to grow and effectively doubles the production of the plant from one stem to two. Repeated harvests insure the fresh leaves are tender and mildly flavoured. If the objective is harvesting for essential oils, the best time to harvest is when flowering is advanced because the oil is more concentrated.

Basil is sold as a fresh leaf, as a dry leaf product, or as a volatile oil and oleoresin. Yields in Ontario are reported to be about 14 tonnes per hectare for fresh material and 1.5 tonnes per hectare for dry. In 2008, recommended basil varieties tested in Saskatchewan produced approximately 2.7 to 3.5 tonnes per hectare of fresh material.

Storage

Basil is damaged by storing at excessively cold temperatures. If put into most fridges, basil will turn black and slimy because of physiological damages directly resulting from the cold. This can be avoided if basil is stored loosely in a container wrapped in a cloth and placed in the crisper. The crisper is the warmest part of the fridge and basil can be kept for up to two weeks.

Basil is hard to dry, although it can be done by following the three principals of drying:

1. Dry in the dark to avoid bleaching (bleaching causes flavour loss);
2. Maintain uniform air movement; and,
3. Keep it warm to reduce the time required to dry.

Varieties for Saskatchewan

A summary of the best performing varieties for Saskatchewan is provided in Table 1.

Table 1. Basil varieties adapted to Saskatchewan ¹

¹Adapted from Recommended Varieties for Saskatchewan Producers, University of Saskatchewan, Department of Plant Sciences.