Grown for its scented flavorful leaves, basil (Ocimum spp.) has many species and varieties. The most commonly grown is sweet basil (Ocimum basilicum). Native to Asia, basil is a tender perennial hardy to U.S. Department of Agriculture plant hardiness zones 9 through 11 and is grown as an annual worldwide. Leaves are used in regional cooking and for fragrances and flavorings. Far from being poisonous, basil flowers are edible and can be used as a salad ingredient or a garnish.
A member of the mint family, basil has square stems and opposite leaves, which can be puckered, smooth, shiny or crinkled. Flowers grow in a terminal spike and are clustered in whorls around the stem. The fragrance and flavor comes from essential oils produced by glands on the leaves, stems and flowers. These oils include sweet-tasting methyl chavicol, linalool with a floral scent and eugenol with the taste of cloves. Different varieties have different combinations of essential oils in the plants. Basil flowers contain the same chemicals present in the leaves, but they have a milder taste.
Basil comes in a number of leaf and flower colors and flavors. Purple-leaved varieties are ornamental in the garden and have darker flower colors. "Red Rubin" (Ocimum basilicum purpurascens "Red Rubin") has deep red-purple leaves with a strong spicy flavor and lavender flowers. Mild-flavored "Purple Ruffles" (Ocimum basilicum "Purple Ruffles") pairs pink to lavender flowers with purple leaves variegated with green. "Ararat" (Ocimum basilicum "Ararat") is a pink-flowered, sweet-tasting heirloom with a licorice flavor. Leaves are green streaked with purple. Green varieties with white flowers include "Genovese," the traditional pesto variety, and "Sweet Green." Pink-flowered "Nufar" is a hybrid resistant to Fusarium wilt. White -flowered "Spicy Globe" (Ocimum basilicum minimum "Spicy Globe") is a compact, small-leaved plant with a strong, spicy flavor.
Typical of the mint family, basil flowers have an upper and a lower lip that surround a tubular throat. The flowers emerge from sepals that are usually the same color as the leaves. Stems of flowering purple-leaved varieties are suitable for floral arrangements. Basil flowers are used to flavor vinegar and oil mixes. Flowers scattered across salad greens or on top of cooked pasta add to the presentation and to the flavor. Flowers from sweeter-tasting varieties are suitable for garnishing fruit salads. The Herb Society of America even mentions candied basil flowers.
Sow seeds outdoors when all danger of frost is over. Grow the plants in full sun for best flavor. Most people grow basil primarily for its leaves, and flower production is secondary. For good crops of leaves, start harvesting stems by cutting them back to the lower one-third of the plant every three to four weeks to increase branching and prevent flowering. When sweet basil begins to flower, leaves become bitter and leaf production stops. If you grow basil primarily for the flowers, allow them to flower without pruning the growth back. Pinch off the flower stems and harvest the individual flowers. These plants will be shorter-lived than those continually cut back for leaf production, so plant seeds for successive crops about three weeks apart.