How to Grow Florence Fennel
Foeniculum vulgare var. azoricum
Florence fennel forms crisp bulbs in full sun and moisture-retentive, fertile, well-drained soil. To reduce bolting, sow after midsummer when days shorten, and keep growth evenly moist. Transplant carefully (or direct sow) and avoid checks. As bulbs swell, earth up or collar to blanch and sweeten. Pick when tennis-ball sized—larger bulbs can go woody. In cold snaps, fleece or cloches help late crops. Use succession sowings for a steady autumn harvest.
When to Start
Sow indoors 4 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 10°C.
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Growth Stages
Approximate days from start
Care Essentials
- Balanced liquid feed fortnightly. Needs consistent moisture to prevent bolting.
- Very bolt-prone. Sow in mid-summer, not spring. Avoid any check in growth — keep well-watered.
Growing Conditions
- Min. soil temperature
- 10°C+
- Germination temperature
- 15–22°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 25 cm |
| Row spacing | 35 cm |
| Sow depth | 0.5 cm |
| Mature height | 60 cm |
| Mature spread | 30 cm |
Sow/plant after last hard frosts; steady moisture prevents bolting.
Pests & Diseases
Pest Aphids
Identification: Clusters of small green insects on shoot tips and developing bulbs, causing distorted growth and sticky honeydew
- Blast off with a strong jet of water
- Spray with fatty acid-based insecticide (check harvest interval for edible crops)
- Encourage ladybirds, lacewings and hoverflies
- Avoid chemical sprays close to harvest on edible crops
Pest Slugs and Snails
Identification: Irregular holes in leaves and damage to the swelling bulb base; slime trails around plants
- Use beer traps or copper tape barriers
- Apply organic slug pellets (ferric phosphate)
- Encourage hedgehogs, frogs and ground beetles
- Ferric phosphate pellets are safe near edible crops
Pest Carrot Fly
Identification: Yellowing foliage and stunted growth; larvae tunnel into the bulb base causing brown scarring and rot
- Cover with fine mesh or fleece barriers at least 60 cm high
- Avoid thinning plants in the evening when flies are most active
- Companion plant with alliums to mask scent
- No chemical controls available for home gardeners on edible crops
Disease Rhizoctonia (Bottom Rot) Rhizoctonia solani
Symptoms: Brown, sunken lesions at the base of the bulb, often with reddish-brown discolouration spreading upwards
Treatment: Remove and destroy affected plants. Avoid replanting in the same spot
Prevention: Ensure good drainage, rotate crops, and avoid earthing up with contaminated soil
Disease Downy Mildew
Symptoms: Yellow patches on upper leaf surfaces with greyish-white fuzzy growth on the undersides
Treatment: Remove affected foliage. Improve air circulation around plants
Prevention: Space plants well, avoid overhead watering, and ensure good airflow between rows
Growing Conditions
| Min. soil temperature | 10°C |
| Germination temperature | 15–22°C |
| Base growth temperature | 6°C |
| Min. daylength to start | 10h |
| Photoperiod sensitivity | long day |
Frequently Asked Questions
- How far apart should I plant Florence Fennel?
- Plant Florence Fennel 25cm apart with 35cm between rows.
- When can I harvest Florence Fennel?
- Florence Fennel is ready to harvest approximately 65 days after transplanting.
- Is Florence Fennel frost hardy?
- Florence Fennel is classified as Half Hardy.
