Basil lovers are devoted to its minty anise flavour and revel in the summer months when their favourite herb is fresh from the garden. And as in all affairs of the heart and stomach, chemistry is a strong influence over the sensory passions. The predominant element in basil's essential oil is linalool, a terpene alcohol with a pleasant taste combined with minty methyl chavicol and clove-like eugenol. Terpenes are hydrocarbons found in essential oils of plants, and their strong scent is also detected in lavender and pinewood. Terpenoids in basil are important anti-cancer hytochemicals—naturally occurring substances that work in conjunction with vitamins and other food nutrients to stimulate protective enzymes and block metabolic pathways associated with the development of cancer and heart disease.
Fusarium Wilt Seeds of sweet basil—and its cousin, mint—sometimes carry fusarium wilt (Fusarium oxysporum) spores. Once the ground in which the spores grow becomes infected, the spores proliferate and cause young plants to wilt when seedlings reach 15 to 30 centimetres tall. Symptoms are brown streaks and discoloured tissue on stems, and sudden leaf drop. There's no chemical treatment for fusarium wilt, but you can avoid it by growing resistant ‘Nufar Hybrid'. If the disease strikes, don't plant basil in that location for several years.
Slugs and snails These pests love the flavour of basil and will search out tender leaves after dark. All the slug-catching methods can be applied to the basil patch, but don't use any chemical slug baits around food plants. Overturned grapefruit rinds and beer traps are useful, and a generous sprinkling of powdered sulfur around the plants will discourage slugs and snails. Nighttime inspections with a flashlight and salt cellar are the most successful method.
Ancient forms of basil originated in Africa and India and are still available. African tree basil (Ocimum gratissimum), sometimes called shrubby or clove basil, is a pungently scented sub-shrub with slightly hairy leaves and delicate white to yellow-green, two-lipped flowers that are tasty in salads. It's a handsomely imposing plant more than one metre tall when container-grown. For medicinal purposes, Africans turn to camphor basil (O. kilimandscharicum), chewing the leaves to release the antibiotic and anesthetic elements. Many of the older species are perennials, hardy to Zone 10 in tropical climates, and ideal as fragrant, edible indoor plants in sunny northern windows. Households in India have a traditional pot of red- or green-leafed Tulasi, or holy basil (O. tenuiflorum), dedicated to the Hindu gods Vishnu and Krishna. Chewing a leaf of holy basil each day is thought to ward off evil spirits and preserve health. Holy basil is believed to guarantee safe passage to heaven, and mourners cast the leaves into graves to ensure the blessing.