Basil is a most useful herb. It is indispensable in Italian cooking, as well as being used in many South-East Asian dishes. Generally, basil is regarded as a 'tender' herb: in other words, it hates cold weather and only grows through the warmer months. Most forms of basil are annual plants, hailing from tropical Asia, Africa and Central and South America. After wonderfully lush growth throughout summer and autumn, the plants gradually lose their vigour, the leaves blacken as winter approaches, and the plant dies off.
There are a number of different varieties of this annual basil (Ocimum basilicum), including the generic 'sweet basil' which is the one we buy bunches of at the greengrocer; other varieties include those marketed as 'Valentino' or 'Lettuce Leaf', which have huge leaves; purple-leaved forms, such as 'Dark Opal' and 'Purple Ruffles'; and Thai basil (Ocimum basilicum 'Horapha'), which can't really be substituted for sweet basil, being much more clove-scented. Greek basil (Ocimum minimum) is a separate species; the plant has tiny leaves and a more compact form. Annual basil loves rich soil, water, fertiliser and sun. It grows about 30 to 60 cm tall. I sow the seed in late August, so that by the time the weather has warmed up sufficiently, the basil is ready to be transplanted outside. I find it best to grow it in a large tub. In my garden, basil is a martyr to the dreaded flea beetle, which disfigures and eventually ruins the foliage, so I place my tubs inside a wooden cage covered with a very fine mesh, which effectively excludes the beetles, as well as moths and butterflies (whose caterpillars also will defoliate basil very quickly), snails and aphids.
Another important aspect of basil culture is to nip out any flowering stems that develop, as these seem to weaken the plant, with all its energy being directed to seed-production if they are allowed to remain on the plant. Regular tip-pruning will help create a shrubby, leafier plant and often obviate the development of flowering stems.
There is much folklore associated with basil. It is said to repel flies - even fruit flies - and mosquitoes; it is also said to 'clear the brain and relieve headaches', as well as to be a digestive tonic if the leaves are mixed with red wine - though I have never personally tested any of these theories. Basil has religious significance in some cultures (particularly holy basil, Ocimum tenuiflorum).
Attempts to preserve basil so as to have it available through winter generally produce substandard results - dried basil doesn't taste much like the fresh herb, nor do chopped leaves frozen in ice blocks, as is sometimes suggested, though they can be useful in casseroles. However, basil can be grown indoors in a pot on a sunny windowsill through winter. Growth is obviously more limited, because of the smaller size of the container required in such a position, and lack of strong sunlight in winter. Basil can also be grown as a microgreen plant on a windowsill (pictured above), thickly sown and harvested a few weeks after germination. The baby leaves have a good basil flavour. Whilst basil is generally grown from seed, some gardeners have success growing it from cuttings.