Vegetable · Bulb vegetable
Fennel
Foeniculum vulgareFlorence fennel forms a crisp, anise-scented bulb at the base of feathery stems, equally good raw or roasted. It is quick to bolt if stressed by cold snaps or long hot days, so timing matters more than for most crops. The one rule: keep it growing fast and unchecked from sowing to harvest.
Sow depth
½ in
Spacing
10 in · rows 16 in
Sun
Full sun
Germination
10–14 days
Time to harvest
65–90 days
Difficulty
Moderate
When to sow fennel
- Sow from around your last expected frost until about 3 weeks after your last expected frost.
- Sow from about 14 weeks before the first expected autumn frost until about 11 weeks before the first expected autumn frost.
Direct sow only — fennel resents root disturbance and bolts if transplanted.Sow thinly in shallow drills once frost risk has passed.Thin seedlings early to their final spacing to avoid crowding stress.
Water evenly — irregular moisture is the top trigger for bolting.Mulch to keep roots cool and conserve soil moisture through the season.Earth up soil around swelling bulbs to blanch them pale and sweet.
Cut at the base — slice the bulb just above soil level with a knife.Harvest once bulbs reach tennis-ball size, before they split or bolt.Leave the stump in place; it often resprouts a flush of feathery fronds.
Companion plants
Fennel releases root compounds that inhibit many neighbors, so it is often best grown in its own bed.
Watch out for
Bolting — Triggered by cold shocks early on or hot, dry spells later. Sow at the right time and keep watering consistent to avoid it.