Step-by-Step Growing Guide
Florence fennel (the bulbing type grown as a vegetable) is notoriously prone to bolting and requires specific timing for success. Sow directly into well-drained, fertile, sandy-loam soil at pH 5.5–6.8 in late spring or early summer — avoid spring sowing as lengthening day length triggers immediate bolting without bulb formation. Thin to 20–25cm between plants in rows 45–60cm apart. Fennel strongly resents root disturbance — direct sowing is essential. Water consistently — 2.5–3.5cm per week — as drought triggers bolting instantly. Feed with a balanced fertiliser at sowing, then a potassium-rich feed at the onset of bulb swelling. When bulbs begin to form above the soil surface (visible swelling at the base), hill soil up around them to blanch them — this produces pale, sweet, tender bulb tissue. Critical: do not plant fennel near dill, coriander, tomatoes, or most herbs — fennel is allelopathic and inhibits germination and growth of most neighbouring plants.
