Sweet Fennel

How to grow Sweet Fennel

Written by the GardenDecoded editorial team · Last reviewed 21 July 2026 · Written for UK gardens · How we research our guidance

Planting

Sow direct in spring, or plant a young plant in a sunny, well-drained spot at the back of a border — the herb form is a perennial that returns each year and reaches shoulder height. Florence fennel, grown for the swollen bulb, is a different proposition: sow it direct after midsummer, as early sowings bolt, and keep it well watered.

Pruning

Cut the whole plant back to the ground in late autumn or late winter. Cutting the flower stems out in midsummer prompts a fresh flush of feathery leaf, at the cost of the seed crop.

Propagation

From seed, sown direct. Established clumps can be divided in spring, though the taproot makes this less reliable than with most perennials. It self-seeds abundantly.

Pests and diseases

Little troubles it. Aphids can gather on the flower heads, and Florence fennel bulbs may rot at the base in cold wet soil.

Value to wildlife

The large flat umbels are among the best border plants for hoverflies, small solitary bees and parasitic wasps in late summer.

Notes

It self-seeds hard — deadhead before the seed ripens unless you want it everywhere. Keep it away from dill, which it crosses with. The bronze-leaved form is the usual garden choice and comes largely true from seed.

This guidance was researched and written by GardenDecoded — see our editorial policy for how guides are checked and reviewed.

Other names for this plant

These names have all been used for Foeniculum vulgare but are no longer the accepted name. You may still meet them on old labels, in books, or in nursery catalogues.

Others in Foeniculum