UC Master Gardeners, Santa Clara County, CA
University of California
UC Master Gardeners, Santa Clara County, CA

Fennel-herb

Garden Help > Herbs

Florence (bulb) fennel, University of Maryland Extension
Florence (bulb) fennel, University of Maryland Extension
Florence fennel is grown primarily for the bulb-like base which is eaten as a vegetable. The leaves and seeds can also be harvested. Common and bronze fennel are grown for the seeds (they do not bulb), but are not recommended in the Bay Area due to concerns regarding invasiveness. Although a perennial, most fennel is grown as an annual for harvesting as bulbs. Fennel will self-sow easily and can take over a garden 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 to plant/propagate

Fennel can handle light frost, and can be grown year-round in milder climates.

  • 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: Not recommended.

Harvesting

  • 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.

Indoors

  • Not recommended

Common pests & diseases

More information

Recommended Varieties for Santa Clara County*

  • Di Parma OP: Superior bulbing fennel, large and uniform, with great flavor. Flowers attract beneficial insects, and swallowtail butterflies will lay eggs on the feathery greens. 24–36" tall. Plant 10–12" apart.
  • Florence

Also, see our list of Spring Garden Market Herbs.

*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.

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