French tarragon is the variety generally considered best for the kitchen, but is never grown from seed as the flowers are sterile, instead it is propagated by root division. It is normally purchased as a plant, and some care must be taken to ensure that true French tarragon is purchased. A perennial, it normally goes dormant in winter. It likes a hot, sunny spot, without excessive watering.
Russian tarragon (A. dracunculoides L.) can be grown from seed but is much weaker in flavor when compared to the French variety. However, Russian tarragon is a far more hardy and vigorous plant, spreading at the roots and growing over a meter tall. This tarragon actually prefers poor soils and happily tolerates drought and neglect. It is not as strongly aromatic and flavorsome as its French cousin, but it produces many more leaves from early spring onwards that are mild and good in salads and cooked food. Russian tarrogon loses what flavor it has as it ages and is widely considered useless as a culinary herb, though it is sometimes used in crafts. The young stems in early spring can be cooked as an asparagus substitute. Horticulturists recommend that Russian tarragon be grown indoors from seed and planted out in the summer. The spreading plants can be divided easily.
A better substitute for French tarragon is Spanish tarragon (Tagetes lucida), also known as Mexican mint marigold, Mexican tarragon, Texas tarrogon, or Winter tarragon. The flavor is stronger than Russian tarragon and does not diminish significantly with age. Though it is a member of the marigold family, the flavor is much more reminiscent of French tarragon, with a hint of anise.