Foeniculum vulgare variety dulce is the botanical name for this half-hardy or biennial, Sweet Fennel. This herb resembles Dill, but its finely divided, anise-scented foliage is light green instead of blue green and its stems are solid, not hollow like Dill's. Sweet Fennel can grow 4 to 6 feet high in flower. The yellow clusters of flowers aren't abundant until the second season, when the plants are sturdy enough to support good seed yields. Foeniculum vulgare variety azoricum is the botanical name for Florence Fennel. This plant resembles Sweet Fennel, but is grown for its edible, swollen leaf base (also called a bulb), which is made up of wide-ribbed, compact solid stems. The finely cut, needlelike foliage looks like Dill, but is apple green in color and has the scent and flavor of anise. The bulbs may be eaten raw or cooked and the foliage may be used as a garnish.

Fennel can live in a variety of soils, but won't do well in dense, soggy clay. Sweet Fennel grows rapidly and needs frequent feedings to grow actively and maintain good color. They should be pruned to keep them thick and at a reasonable height. If you aren't growing them for seeds, cut off the flowering stems. Spring sown Fennel will be large enough to harvest the leaves by the summer of the first season. The leaves may be used fresh in salads or to garnish fish entrees. For Fennel seeds, cut off the large individual seed heads when they begin to turn color, and dry them. Plants may lose vigor and die if you allow too many seed heads to remain. Florence Fennel grows best in cool weather. They should be grown as a cool-season annual. Even though it is half-hardy, late spring freezes can kill unprotected seedlings. The whole plant is pulled up at harvest. Trim off the stems, ½ to 1 inch from the bulb. The larger stems can be chopped and cooked with the bulb and the foliage may be used for garnishing.

Sweet Fennel can easily be increased by direct seeding. Florence Fennel is started early indoors, in the North, in peat pots. Seedlings are transplanted to the garden, after they are hardened off, 2 to 3 weeks before the frost-free date. They should be set 6 to 12 inches apart. Even though Florence Fennel is half-hardy, late spring freezes can kill unprotected seedlings. In mild climates, seeds may be sown in late summer. In good conditions, bulbs usually size up before winter. Some gardeners pull loose soil up around the bulbs to blanch them.

Sweet Fennel -
 
Foeniculum vulgare dulce,
 
Florence Fennel -
 
 Foeniculum vulgare azoricum; Romano Precoce (an early variety).