When to Harvest Fennel

Known since ancient times and a regular player in Mediterranean diets, fennel (Foeniculum vulgare) is an aromatic vegetable and herb that is grown for its foliage, seed and fleshy white bulb. Though grown as an annual in most climates, the plant is considered a short-lived perennial weed in warmer zones. Often erroneously referred to as anise due to its licorice-like flavor, fennel is unrelated to flowering anise (Agastache foeniculum).

Fennel can be grown from seed or set out as transplants as soon as danger of frost has passed. In areas where summers are long and hot, seed should be started indoors and plants put out as soon as possible in order for the bulb to have time to form before hot weather sets in. Cooler-climate gardeners can direct-sow seed into the garden and harvest at the beginning of summer; soaking seed for several days improves germination. Sow seed and thin plants to 12 inches apart after they reach several inches in height.

Befitting of a Mediterranean native, fennel can withstand drought, but performs best in loamy, well-drained soil rich in organic matter. Fennel is resistant to most common pests and diseases of the home vegetable garden, but powdery mildew may be problematic with cool weather. Aphids can also be an issue. Fennel withstands light frosts, but hard freezes kill the plant. Choose a location carefully: Fennel reportedly inhibits the growth of tomatoes, and cross-pollinates with dill.

With the proper location in the garden and good care, fennel is generally ready for harvest within three months of planting from seed, or 70 to 80 days from transplants. Harvest bulbs when they reach roughly the size of a tennis ball or before the plant begins to flower. With a sharp knife, harvest the bulb by cutting the plant off from its taproot at the base of the soil. The foliage as well as stems are also edible. If seed is desired, allow the plant to flower and the seedheads to dry and turn completely brown before harvesting. Harvest the flowers before the capsules open to disperse the seed.

As members of the Apiaceae plant family, the flowers of the fennel plant are irresistible to bees and other pollinating nectar insects. Along with parsley and dill, try planting fennel simply for its value in attracting beneficial insects to the garden. Butterfly enthusiasts also know that fennel is a host plant for the caterpillar of the black swallowtail butterfly. In the kitchen, use whole seeds to season Italian sausage, include the feathery foliage in salads or as a vinegar flavoring, and braise or steam the bulbs along with other vegetables and poultry for a healthy, aromatic feast.