Basils (Ocimum basilicum) belong to the mint family (Lamiaceae) and have the square stems, two-lipped flowers and abundant fragrance-bearing oil glands typical of mint.
The name, Ocimum basilicum, comes from the Greek okimon (smell) and basilikon (royal). Basils of the basilicum species, which provides most of the culinary varieties, are extremely variable in height, leaf size, color and form.
Large-leaved green basils, such as sweet basil, Italian basil, and lettuce-leaf basil, can grow 2-3 feet in height. Small-leaved green forms such as dwarf basil, bush basil, or ‘Spicy Globe’ will grow 8-12 inches in height and as broad. Reddish-purple variations such as ‘Dark Opal’ or ‘Purple Ruffles’ tend to be intermediate in size, bearing purple instead of white flowers. These variants have minor nuances of flavor, and are used for the same purposes.
Novelty basils, named for their fragrance, have some culinary use and are worth taste testing for individual preferences; you may find plants offered as cinnamon, licorice or anise basils. Lemon basil (Ocimum xcitriodorum) is a white-flowered, smaller-leaved plant with a pronounced lemon fragrance.
Many of the culinary basils are tender annuals in most of the U.S., though perennial in warm temperate and tropical regions. They are easily grown from seed, from cuttings which root quickly in water, or from purchased plants, providing the soil has warmed to 70°F, the day length is long enough, and the weather has settled (the nights are not below 55°F).
Basil should be pruned when it has three to five sets of true leaves to promote branching and maximize growth. For the first pruning, cut the plant back to just above its second set of leaves. Young leaves should be cut throughout the summer for freezing and drying or making oils, butters, pesto and vinegar. Older leaves have less oil content and become tougher. Though basil is heat-loving and will grow strongly all summer, as soon as nights go below 50°F it shows signs of deterioration.
The flavor of fresh leaves is outstanding in salads, with tomatoes, eggplant, peppers or zucchini, in marinades, as a sandwich garnish, and in the classic pesto sauce. Cooked briefly, it is a flavorful addition to soups, stews, and sauces. It works well with most other herbs. To insure best flavor, add to salads and cold dishes soon after cutting and to cooked dishes in the last few minutes of cooking.
Basil can be used as an ingredient in potpourri, and the essential oils are used in perfumery. It is also used commercially as a flavoring agent in foods and pharmaceuticals, and has been used in traditional folk medicine in countries around the world.
Source: Herb Society of America