Perennial herbs, once established, will live for several years. In northern areas, some perennials such as rosemary and bay, must be protected in winter or treated as annuals. In addition to rosemary and bay, other perennials include mint, thyme, chives, oregano, sage, and tarragon. Annuals may be started from seed or transplants each year. Anise, basil, borage, chervil, coriander, sweet marjoram, and summer savory are all annuals.
Some herbs are biennials, producing flowers and seeds their second year of growth.
Parsley and caraway are biennials. Rosemary, oregano, marjoram, and thyme are difficult to grow from seed because of slow or poor germination and are best propagated from cuttings or root divisions. When you plan your herb garden, you should take into consideration the growth habits of the herbs you intend to grow. Wormwood and members of the mint family are aggressive growers. Mint can grow up to three feet tall, spread quickly, and take over a small garden in one growing season.