Carrot

Daucus carota subsp. sativus · cultivated carrot

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At a Glance

The carrot (Daucus carota subsp. sativus) is one of the most widely grown root vegetables in British gardens and allotments. It is the cultivated form of wild carrot, bred over centuries for a swollen, sweet, tender taproot in place of the tough, pale root of its wayside ancestor. Carrots are sown direct, crop over a long season, and store well into winter — but they reward attention to two things above all: a deep, light, stone-free soil, and protection from carrot fly. This guide covers growing them successfully across the range of UK conditions.

Choosing the right type

Carrots are grouped by root shape and season, and choosing the right group for your soil and sowing time matters more than the individual cultivar:

• Amsterdam & Nantes — quick, slender, sweet early carrots for the first sowings and for shallower soils.
• Chantenay — short, stumpy, broad-shouldered roots that cope better with heavier or shallower ground.
• Autumn King & maincrop types — large, late roots for storing through winter; they need the deepest soil and the longest season.

On heavy, stony or shallow ground, choose the short-rooted Chantenay or round 'Paris Market' types rather than fighting to grow long maincrops. Cultivars sold as carrot-fly resistant (such as 'Resistafly' or 'Flyaway') are a useful extra defence, though no carrot is wholly immune.

When and where to sow — across the UK

Carrots are hardy and sown direct where they are to grow; they resent transplanting, as disturbing the root tip causes forking. Timing depends on where you garden:

• Early sowings under cloches or fleece can start in February in the mild south-west and southern England, where the soil warms early.
• Maincrop sowings run from April to early July across most of the country.
• In the north of England, Scotland and exposed or upland gardens, hold off until the soil reaches about 7 °C — typically late April into May — as carrot seed germinates poorly in cold, wet ground.
• Successional sowing every three to four weeks gives a continuous supply rather than a glut.

Carrots need an open, sunny site and, above all, a deep, light, free-draining soil — ideally a sandy loam. Do not grow them on freshly manured ground: excess nitrogen and stones both cause roots to fork and split. On heavy clay or stony soil, grow short-rooted types, build a raised bed of sieved soil, or sow in deep containers of loam-based compost.

Sowing and thinning

Sow thinly, about 1 cm deep, in drills 15–30 cm apart, and water the drill before sowing in dry weather. Germination is slow — two to three weeks — so mark the rows. The hardest discipline is thinning: thin seedlings to about 5–7 cm apart, ideally on a still, damp evening, and remove the thinnings from the plot entirely, because the bruised foliage releases the scent that draws carrot fly. Sowing thinly enough to avoid heavy thinning is the single best way to reduce that risk.

Carrot fly — the key pest

Carrot fly (Psila rosae) is the one problem that defeats most first-time carrot growers. The low-flying female is drawn by the smell of carrot foliage and lays eggs at the base of the plants; the larvae tunnel into the roots, leaving rusty galleries that ruin the crop. UK-appropriate control is about exclusion and avoidance rather than spraying:

• Cover the crop with horticultural fleece or fine insect-proof mesh from sowing, sealed at the edges — the most reliable defence.
• Erect a barrier: the fly travels low to the ground, so a 60–75 cm vertical fence of fleece or mesh around the bed keeps most out.
• Avoid bruising the foliage — thin sparingly, in the evening, and clear thinnings away.
• Time sowings to dodge the main egg-laying periods (roughly May and again in August), or grow resistant cultivars.

Caring for the crop

Once up, carrots need little feeding — rich soil harms root quality. Keep the bed weed-free while seedlings are small, as they compete poorly, and water steadily in dry spells: a sudden drink after a drought makes swelling roots split. Earth up or cover any shoulders that push above the soil and turn green. Carrots have no need of staking or training.

Harvesting and storing

Pull early carrots as soon as they are finger-thick — usually 12–16 weeks from sowing. Maincrops can be left in the ground and lifted as needed; in milder districts they hold through winter under a thick mulch of straw or bracken. Where the ground is heavy, wet or hard-frozen — much of the north and Scotland — lift maincrops by late autumn and store them in boxes of just-damp sand in a cool, frost-free shed, where they keep for months. Twist or cut off the tops before storing.

Common problems

Besides carrot fly, the usual troubles are cultural. Forked or split roots come from stony ground, fresh manure, or transplanting. Green shoulders are caused by light reaching exposed root tops — earth them up. Poor or patchy germination almost always means soil that was too cold or too dry at sowing. Splitting follows irregular watering. Get the soil and the sowing time right, keep the fly out, and carrots are among the most rewarding and trouble-free crops in the British kitchen garden.

Cultivars and Varieties

Pests and Diseases

For step-by-step help, read Dealing with Slugs and Snails. Or browse the full plant problem solver to diagnose an issue by symptom.