How to grow Fennel (Herb)

Where to plant

Fennel grows best in full sun in moist, organically rich, well drained soil, and tolerates clay, sand and, once established, drought. It grows across a wide range of climates.

It self seeds freely and has escaped gardens and naturalized in many areas. In California, the California Invasive Plant Council rates wild fennel (Foeniculum vulgare) as a moderate invader of grasslands, coastal scrub, riparian areas and wetlands, while noting it is unclear whether culinary varieties are invasive. Wherever you garden, and especially near wild land in California, remove spent flowers before seed forms.

In Florida, the Gulf South, Texas, the desert and Southern California, sow from fall to late winter. In the Mid-South and Mid-Atlantic, sow in late winter to spring and again in late summer. Across the North, the Midwest, the Mountain West and Alaska, sow in spring after frost.

Choosing a variety

Green herb fennel is grown for its leaves and seed. Bronze fennel (Purpureum) has purple bronze foliage and is just as useful in the kitchen and very ornamental. For crisp, mild bulbs, grow Florence fennel varieties instead.

How to plant

1. Sow seed directly where it is to grow; fennel has a taproot and dislikes transplanting.
2. Sow about a quarter inch (6 mm) deep and keep the soil moist until seedlings appear.
3. Thin to about 12 inches (30 cm) apart.
4. Plant fennel in its own corner of the garden, away from the vegetable beds.

Watering and feeding

Water regularly until plants are established. Mature fennel tolerates drought, though leaves stay more tender with steady moisture. Avoid poorly drained soil, which causes stem and root rot.

Fennel needs little fertilizer in soil with some compost.

Pruning and care through the year

• Cut off spent flower heads before seed forms unless you are harvesting seed, to stop it spreading.
• Leave some swallowtail caterpillars; fennel is one of their host plants.
• In mild areas, cut plants back to the base in late winter and they regrow as perennials.

Harvesting

Snip leaves as needed once plants are well established and use them fresh with fish, eggs and salads. The yellow flowers are edible too.

For seed, cut the flower heads when the seeds turn from green to tan, dry them upside down in a paper bag, then rub out the seeds and store them airtight. Harvesting all the seed heads also keeps fennel from spreading.

Growing in pots

Fennel can grow in a large, deep pot at least 12 inches (30 cm) wide and deep for its taproot, in full sun. A pot also keeps it from self seeding into the garden if you remove the flowers.