Florence fennel
Foeniculum vulgare
Last edited on 28 Oct 2026. View history
Fennel
How to sow fennel: Direct seed outdoors, or sow indoors and harden off before transplanting outside
Sun requirement for fennel: Plant in Full Sun
Fennel is a flowering plant species with yellow flowers and feathery leaves. It is grown primarily for its bulbous white base and green leaf stalks, which have a mild, fresh licorice flavor. It's base and stalks are delicious roasted, grilled, or eaten fresh.
Do not let fennel go to seed: it can become invasive.
- 9
- plantings
- 0
- harvests
- 4
- seed packets
Fennel facts
Lifespan
Annual
living and reproducing in a single year or less
46 weeks
median lifespan
Height 脳 spread
60cm 脳 60cmRow Spacing
15cmWhat are growing degree days?
A plant grows with warmth, not with days. A growing degree day is one day's worth of useful warmth: how many degrees the day's average temperature is above the lowest temperature the crop grows at. Add them up from planting and you know how far along the crop is, whatever the calendar says.
Say that lowest temperature is 10掳C. A day averaging 17掳C gives 7 growing degree days. A day averaging 8掳C gives none, as it is too cold for the crop to grow. That is why the same lettuce takes about 50 days in a summer and 90 in an autumn: it needs the same total warmth either way.
For fennel, the FAO EcoCrop database gives a lowest growing temperature of 6掳C and a shortest growing cycle of 30 days at its best temperature, about 420 growing degree days to a first harvest.
Where you've told us where your garden is, we use this and the weather there to predict when your fennel will be ready to harvest. We don't use it for how long a plant lives or when it finishes: we go by what members have logged for that.
Growing fennel
- Sow seeds in modules 4 weeks before planting out
- Dig compost into the bed 1 week before planting out
- Set or refill beer traps for slugs and snails at planting out every week
- Water regularly at planting out every week
- Earth up around the bulbs 6 weeks after planting out
- Cut the bulbs above the root at first harvest
- Pull out plants that have bolted 4 weeks after first harvest
How members grow fennel
Sunniness
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Planted from
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Varieties of fennel
Photos
PhotosFennel crops
Fennel plantings
Video
Where fennel grow
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What people are saying about fennel
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Who's planted fennel
- flatfood balcony farm 路 Bangalore, Southern...
- milki Perimeter Yard 路 San Francisco Bay Area
- gregoryo Bed 2: driveway 路 Osborne Park, Western...
- jinty Kitchen garden 路 Oxford, uk
- juliet Back garden 路 London, UK
flatfood
Fennel harvests
Nobody has harvested this crop yet.
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Ecological requirements
Data from the FAO EcoCrop database for Foeniculum vulgare Mill.
| Family / Taxonomy | Magnoliopsida Rosidae Apiales Umbelliferae |
|---|---|
| Optimal temperature | 15 - 25 掳C |
| Absolute temperature | 6 - 32 掳C |
| Killing temperature | growth: -2 掳C, rest: -5 掳C |
| Optimal rainfall | 700 - 1500 mm/year |
| Absolute rainfall | 300 - 2600 mm/year |
| Optimal soil pH | 6.5 - 7.5 |
| Absolute soil pH | 4.8 - 8.2 |
| Crop cycle | 30 - 110 days |
| Max altitude | 2500 m |
| Life form | herb |
| Life span | biennial, perennial |
| Habit | erect |
| Optimal soil depth | medium (50-150 cm) |
| Optimal soil texture | medium |
| Optimal soil fertility | high |
| Optimal soil drainage | well (dry spells) |
| Optimal soil salinity | low (<4 dS/m) |
| Photoperiod | long day (>14 hours) |
| Optimal light | very bright |
Learn more about fennel
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