Florence fennel is grown for its plump, crisp bulb and gentle aniseed flavour, rather than for herb fennel's leaves and seed. It makes an excellent autumn vegetable where summers are warm enough, but it dislikes disturbance, drought and early sowing, all of which encourage flowering.

When and how to sow

For dependable bulbs, sow Florence fennel from June to July, either directly into warm soil or in modules to minimise root disturbance. Choose a sunny, sheltered bed with fertile, free-draining soil improved with garden compost. Thin or plant seedlings 30 cm apart, allowing room for each base to swell. A late sowing is especially useful in southern gardens; northern gardeners should use the earliest June window.

Care

Keep plants evenly watered and weed-free so growth remains continuous. Mulch lightly in dry spells, avoiding burial of the growing point. When bulbs begin swelling, draw loose soil around their bases to keep them pale and tender. Avoid rough transplanting or sudden feeding changes, which can trigger bolting.

Common problems

Bolting is the chief difficulty: long days, cold checks and dry soil can produce flower stems instead of bulbs. Sow at the recommended time and water consistently. Aphids may gather on foliage, while wet, crowded ground can cause rot; provide spacing, remove affected material and avoid waterlogging.

Harvest

Lift or cut bulbs when they are firm and roughly fist-sized, usually from September into October, before they become loose or elongated. Slice just below soil level and trim off the tall stems, retaining tender fronds if wanted. Use bulbs soon after picking, as their crispness declines in storage.

Growing Fennel: frequently asked questions

When should I sow fennel in the UK?

For dependable bulbs, sow Florence fennel from June to July, either directly into warm soil or in modules to minimise root disturbance.

What are common problems when growing fennel?

Bolting is the chief difficulty: long days, cold checks and dry soil can produce flower stems instead of bulbs.

When is fennel ready to harvest?

Lift or cut bulbs when they are firm and roughly fist-sized, usually from September into October, before they become loose or elongated.

General guidance for UK home gardens and allotments. Reference figures are typical values; your exact timing depends on your region, last-frost date and variety. Page updated 19 Sep 2026.