Pelham GardensGrow What Matters

Florence Fennel

A UK garden challenge worth taking on. Sow late to dodge bolting and you'll get crisp, aniseed-sweet bulbs from a crop most gardeners never quite crack.

Written by Yemi · Last reviewed August 2026

Maturing this month
First sprouts in 10–14 days

Difficulty

Florence Fennel

Florence Fennel should be ready to harvest this month. Check for size and colour.

Growing Calendar

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Sow
Transplant
Harvest

This month: Sep

Log to journal

Ready to harvest now

  • Check size and ripeness
  • Harvest regularly
  • Store or use fresh

Sowing Guide

What you'd find on the seed packet

Sow Depth

1cm

Spacing

30cm

Germination

10–14days

Thinning

Thin to 30cm apart, or sow direct in modules to avoid disturbing roots

Grower's Note

Timing is everything. Sow too early and cold, lengthening days trigger bolting instead of a bulb. Wait until late May or June even if it feels late compared to other crops.

Recommended Varieties

'Dragon' holds an RHS Award of Garden Merit and has real resistance to bolting and yellowing, the safer choice on an exposed or inconsistent plot. 'Rondo' also holds an AGM and is the faster cropper, producing uniform bulbs early enough to grow under cover. For organic growing, The Organic Gardening Catalogue lists 'Romanesco' as an open-pollinated Italian heirloom alternative, producing large sweet bulbs from a later sowing.

Planting Out Guide

Best spaces, conditions and how to plant out

Plant Spacing

30cm

Best Grown In

Open ground, large containers, raised beds

Conditions

Full sun. Fertile, moisture-retentive soil. Keep consistently watered, especially as bulbs begin to swell.

Grower's Note

Earth up around the base of the swelling bulb, much like celery, to keep it pale and sweet rather than green and tough. Grow away from other vegetables where possible.

Growing Stages

Approximate weeks from sowing to harvest

Sprouting

2wks

Seeds germinate and first leaves emerge. Keep warm and moist.

Establishing

8wks

Root system develops and plant builds structure. Pot on if needed.

Maturing

14wks

Plant reaches full size and begins producing. Harvest at peak.

Total~24 weeksfrom seed to harvest

Companion Plants

Plant these nearby for natural pest control, better yields, and healthier soil.

Climate Control

Today

C

Humidity

%

Water

Daily

Sunlight

6+ hours direct sun

Watch Out For

Bolting is the defining risk: plants that experience a cold snap or long days early on will run to flower instead of forming a bulb. Never sow before late May

Slugs target young seedlings hard. Protect with copper tape or torchlit evening patrols until plants are established

Irregular watering causes bulbs to split or stay small. Keep the soil consistently moist, especially once bulbs begin to swell

Pests & Problems

Full guide

Slugs

Young seedlings shredded or disappearing overnight

Jun–Aug

Aphids

Small clusters on the feathery foliage

Jun–Aug

What You'll Need

Equipment for growing florence fennel

Modular Seed Tray

96-cell for precision sowing

Fine Rose Watering Can

Gentle shower for seedlings

Bamboo Canes

Pack of 20 × 120cm

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Grown Organically

Every method in this guide works with natural systems: no synthetic chemicals, no shortcuts.

Read our approach

Common Questions

About growing Florence Fennel in the UK

Why has my fennel bolted instead of forming a bulb?

Bolting is almost always caused by sowing too early. Cold snaps combined with the long days of spring trigger flowering instead of bulb formation. Wait until late May or June to sow, even though this feels later than most other crops.

What's the difference between Florence fennel and the herb fennel?

Florence fennel is grown for its swollen, aniseed-flavoured bulb at the base of the plant and is treated as an annual vegetable. Herb fennel is a perennial grown for its feathery foliage and seeds, and doesn't form a bulb at all.

Does fennel grow well alongside other vegetables?

Not particularly. Fennel is known to inhibit the growth of many neighbouring plants, including beans and tomatoes. It's usually best grown in its own dedicated patch, away from the main vegetable beds.

How do I keep fennel bulbs pale and tender?

Earth up loose soil around the base of the bulb as it swells, similar to blanching celery. This keeps it pale, mild and tender rather than green, tough and overly aniseed-flavoured.

Written from real growing experience, not just research. Read the story behind Pelham Gardens.

Member guides

There's more to growing Florence Fennel than this guide covers.

A Garden Journal to log what worked, a personalised sowing planner in My Garden, and monthly reminders timed to the calendar.

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