Florence fennel is grown for its swollen leaf bases or ‘bulbs’ and edible leaves. It can be tricky to grow successfully and needs warmth and consistent moisture. The succulent bulbs are well worth the effort and have a delicious sweet flavour with a hint of aniseed.
Jobs to do now
- Sow seeds outdoors
- Keep plants well watered
- Feed with a high potassium fertiliser
Month by month
Florence fennel grows best during warm summers and needs an open, sunny site with fertile, moist but well-drained soil. Add plenty of organic matter, such as well-rotted manure or garden compost, to the soil, ideally the winter before sowing.
Fennel dislikes root disturbance, so sow either direct outdoors or singly into modules indoors.
You can sow outdoors from late spring to mid-summer, 15mm (½in) deep, in rows 30cm (1ft) apart. Thin out the seedlings to 30cm (1ft) apart when the soil is warm, from May to early July, but take care not to disturb the roots of the remaining plants. Use bolt-resistant cultivars for mid-June to mid-July sowings.
Fennel can also be sown outdoors in large containers filled with multi-purpose compost.
In cooler climates or for early crops, you can sow seeds singly in modules in a greenhouse or on a warm windowsill. Sowing one seed per module avoids pricking out and means the young plants can be transplanted outdoors with minimal root disturbance. Early sowings are very liable to flower prematurely (bolt), so choose a bolt-resistant cultivar.
Plant out the modules once the soil is warm and there is no danger of frost, from early May onwards. Gradually acclimatise plants to outdoor conditions (harden off), before planting out.
Provide plenty of moisture consistently throughout the growing season, keep the area weed free, and add a mulch of garden compost to the soil to hold in moisture.
Feed with a high potassium fertiliser every two weeks once established.
The largest bulbs are formed in warm, sunny, moist summers.
Earth up (mound soil) round the bulbs as they start to swell, from mid-summer until mid-autumn, to blanch them and protect them from early autumn frosts.
Florence fennel can be harvested in late summer and autumn, when the swollen bulbs are 7–10cm (3–4in) across.
Cut the bulbs off at ground level, leaving the roots, which should then send up small shoots that can be used in salads.
Plants flower and set seed prematurely.
Unless growing for seed sow bolt-resistant varieties. Sow or plant at the correct time and keep the soil or compost moist.
Slugs and snails
These feed on the young seedlings and you'll see the tell tale slime trail on the soil around your crop, as well as on the leaves.
There are many ways to control slugs and snails, including beer traps, sawdust or eggshell barriers, copper tape and biocontrols.
When using Florence fennel raw in salads, the mild flavour can be enhanced by slicing the bulb and putting it in a bowl of water and ice cubes, then placing in the fridge for an hour.
You can also add the leaves as a garnish to salads or infuse them in vinegar.
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