The Basics
There are two types of fennel:
- 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 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, fennel is usually grown as a cool season annual for harvesting as bulbs. If allowed to flower, 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. 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: Fronds of bulbing varieties typically reach 12 to 30 inches tall before harvesting, but will get taller if allowed to bloom and go to seed. Common and bronze fennel can get as tall as 4 to 5 feet.
When to plant
- Direct seed in February to April, possibly May, or September to October, possibly August
- Transplant in February to April, possibly May, or September to October, possibly August
- If growing your own seedlings, start the seeds 6 weeks before you want to plant
- Plant 8 to 12 inches apart
Harvest window
- Harvest the bulb-like base when it is large and plump, 4–6 inches 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.