Fennel

Garden Help > Vegetables

The Basics

Florence (bulb) fennel, University of Maryland Extension

• Florence fennel, also called bulbing fennel: grown primarily for the bulb-like base of the stalks which is eaten as a vegetable. Leaves and seeds can also be harvested.
• Common and bronze fennel: grown just for the seeds or foliage (they do not form succulent bulbs), but are not recommended in the Bay Area due to concerns regarding invasiveness.

Overview

• Although a perennial, most fennel is grown as a cool season annual for harvesting as bulbs.
• Fennel, even bulbing fennel, will self-sow easily and can take over an area if not controlled.
• Fennel attracts many beneficial insects and is a host plant for swallowtail butterflies.
• There are many culinary uses for fennel from around the world; enjoying the bulb as a vegetable, fronds as an herb, and seeds and pollen as spices.
• In grocery stores, fennel is sometimes labeled sweet anise, but anise seeds come from a totally different plant, Pimpinella anisum.

How to grow

• Type: Cool season perennial, but usually grown as an annual
• Light: Full sun
• Soil: Well amended soil, good drainage
• Water: Regular watering, likes moist soil
• Size: Florence varieties typically 12-36" tall; common and bronze can get as tall as 4-5'. Plant Florence varieties 8-12" apart

When and how to plant

• From seed: Sow seeds February-April (maybe May), September-October (maybe August). If growing from seed for transplants, allow 4 weeks to be ready
• Transplants: February-April (maybe May), September-October (maybe August)
• Cuttings: No
• Spacing: 8–12 inches apart

Harvest window

• Harvest the bulb-like base when it is large and plump, 4–6" across, typically 60-90 days after transplanting. Cut just above the soil line.
• Pollen can be collected from flower blooms by shaking flower heads into a plastic bag.
• Pick leaves at any time during the growing season. Do not remove more than 1/3 of the foliage.
• Harvest seeds when flower heads turns brown. Cut the seedheads and place in a paper bag in a cool, ventilated, location. The seeds will fall off when dry and can then be collected.

Common pests & diseases

• 
  Aphids
• Thrips
• Cabbage moth larvae
• Anise swallowtail larvae (pictured): While the butterflies are welcome and damage from the larvae eating the foliage is negligible on mature plants, young seedlings can potentially be overwhelmed. Pick off as needed.

More links

• Fennel in the Garden, Utah State Extension
• Fabulous Fennel UC Master Gardeners of Sonoma County

Recommended Varieties for Santa Clara County^*

• Di Parma OP: Superior bulbing fennel, large and uniform, with great flavor

^* Many other varieties may also do well here in Santa Clara County. This list is based on UC Master Gardener trials, taste tests, and feedback from local growers.