How to grow fennel

Fennel is grown for two things at once: feathery, licorice-scented foliage and seed used in cooking, and, in bulb types, a swollen base at the soil line. It grows into tall, airy clumps that stand out in a bed and produce broad heads of tiny yellow flowers by late summer. Those flowers draw swallowtail butterflies, whose caterpillars can strip a plant of foliage over a few days, though established plants generally recover. Gardeners grow it for the licorice flavor found in every part of the plant.

Fennel's hardest habit to manage is its tendency to self-seed. North Carolina State University Extension notes the plant freely self-seeds and has escaped gardens to naturalize in parts of the country. A second-year gardener who leaves spent flower heads standing for pollinators, or forgets to cut them before they shatter, finds seedlings coming up in paths and neighboring beds the following spring, regardless of what was planted there. Because the seedlings share that scent and a taproot that resists pulling, a bed can end up fighting volunteers for several seasons after one year of unchecked flowering.