Aromatic herb to 34 feet tall. Soft, feathery leaves; umbrellalike, 6 inches-wide clusters of small yellow flowers. The seeds and leaves have a pungent fragrance. Sow seed where the plants are to be grown; for a constant supply, sow several times during spring and summer (germinates and grows better in spring than in summer). Thin seedlings to about 1 feet apart. An easy way to grow it in a casual garden is to let a few plants go to seed. Seedlings appear here and there at odd times and can be pulled and chopped for use as seasoning. Use seeds in pickling and vinegar; use fresh or dried leaves in cooked dishes, salads, sauces, as garnish. Caterpillars of black swallowtail butterflies often feed on the foliage.