Fennel

Herb fennel (Foeniculum vulgare) has feathery, yellow-green foliage with a sweet, mildly anise or licorice flavor. It is grown for its leaves and seeds and reaches 3 to 5 feet (91 to 152 cm) tall.

Sources differ on how long the plant lives. One describes it as a perennial that is normally grown as an annual, another as a short-lived perennial often grown as an annual in cooler climates, and a third as technically a biennial that often flowers only in its second year.

The flowers are tiny and yellow, and they attract bees, butterflies and other beneficial insects. Florence fennel, which is grown for its enlarged leaf bases, is a different form covered separately.

Sowing. Direct sow herb fennel seed in the garden after the danger of frost has passed. Sow about ¼ inch (0.6 cm) deep after the last spring frost. Seeds usually germinate in 7 to 10 days, though another source says 1 to 2 weeks.

Transplanting. Starting indoors is treated differently by different sources. One says plants can be started indoors 4 to 6 weeks before the last spring frost and transplanted before they become rootbound. Another says starting plants indoors is generally not recommended because of the taproot, and a third says it does not transplant well.

Spacing. Sources give different thinning distances. One says to thin to 4 to 6 inches (10 to 15 cm) apart, while another says 10 to 12 inches (25 to 30 cm) apart.

Site. Choose a spot in full sun, meaning at least 6 hours of direct sunlight a day. It does best in moist, well-drained soil with plenty of organic matter, and it tolerates clay and sandy soils.

Watering. Keep the soil consistently moist while plants are establishing and during long dry spells. Once established, the plant is drought tolerant. Roughly 1 inch (2.5 cm) of water per week from rain or irrigation is recommended.

Mulch and feeding. Mulch with shredded bark, compost or untreated grass clippings to conserve moisture and suppress weeds. Avoid heavy fertilizing, since lush growth often has less flavor.

Support. In windy areas, plants grown in fertile soil may need staking.

Self-seeding. The plant readily reseeds. In mild climates it can become invasive, while in cooler climates it rarely escapes cultivation. To prevent spreading, remove spent flowers and stems before seed forms.

Aphids may infest stems and flower heads, especially as plants begin to bloom; a strong spray of water can wash them off. Slugs can also be a problem.

Stem and root rot can occur in poorly drained soil. Powdery mildew may develop when air circulation is poor or the plants are overwatered.

Black swallowtail caterpillars often feed on the foliage. They can eat a lot of leaves but rarely cause lasting damage.

Harvest the feathery leaves as needed once plants are established. The stems of tender flower stalks just before they bloom are considered the best for eating.

For seed, let the flower heads turn light brown, then cut them and place them in a paper bag to finish drying. The seeds separate from the heads as they dry.

Fresh foliage can be refrigerated for short-term storage, and for longer storage it can be frozen or dried. One source says the leaves do not keep their flavor well when dried, while another says properly dried herbs keep their quality for many months.

Store dried seeds in a moisture-proof container.

Pets: fennel is listed as non-toxic to cats and dogs. Eating small amounts mixed into food is considered low risk, but concentrated oil should be avoided.

People: the plant sap can cause skin irritation in sensitive people, especially when skin is exposed to sunlight.