UK crop guide
Carrots are sown where they will crop. Transplanting forks the roots. The RHS puts the main outdoor season from April to early July, with early varieties possible in February or March if you cover them with a cloche or fleece.
A stony or heavy clay soil twists long roots. Use a short or round variety there, or sow into a deep container of peat-free compost. Sandy, deep beds can take the long types.
Rake the bed fine and pick out stones. Make a drill about 1cm deep, water the bottom, and sow thinly. Space further rows 15 to 30cm apart. Germination is slow, so do not assume a quiet row has failed after a week.
Sow a short row every three to four weeks rather than one long row. Thin to 5 to 7.5cm if the seedlings are crowded. Thinning and weeding both release the carrot smell that draws carrot fly, so do it on a still evening and put the mesh straight back.
The RHS found that a complete cover of insect-proof mesh is the most effective way to stop carrot fly. Sowing after mid-May misses the first generation of the fly. Lifting the crop before late August misses the second. You cannot do both with one sowing, which is another reason to sow in batches.
Baby roots can be ready in four to six weeks, and a useful carrot in about 12 to 16 weeks. Pull them once they are large enough to eat. The RHS notes that flavour drops if you chase the biggest root, especially from spring sowings.
Maincrop sowings can be left in the ground into winter. In late autumn, cut the tops off and cover the row with straw or cardboard so you can still lift roots in a frost. If your soil sits waterlogged, lift them and store the sound roots in a box instead.
The larvae tunnel into the root and the damage then rots. Cover the whole bed with insect-proof mesh, from sowing onwards. Avoid a recently used carrot bed, because eggs may still be in the soil. A few varieties have some resistance, but a cover is the reliable part.
Stones, fresh manure and root disturbance all split the root. Sow direct, into a fine bed, and choose a short variety if your soil is heavy.
A drought followed by a soak splits the root. Carrots rarely need water in the ground, but a thorough drink every couple of weeks in a long dry spell keeps them growing evenly. Containers dry out faster and need more regular watering.
Kit for this crop, based on the method above.
For early sowings and for covering tender plants if a late frost is forecast.
Useful for warming a row before you sow, and for protecting early carrots and salads.
The RHS found a full cover is the most effective defence against carrot fly, and it also keeps pigeons and caterpillars off brassicas.
For lifting roots and potatoes without spearing the crop.
A fine rose avoids washing small seed out of the drill.
Variety and sowing date, so succession sowings do not get mixed up.
It is better not to. The RHS says moving them disturbs the root and leads to forked or twisted carrots. Sow them in the row or in the container where they will grow.
A sowing after mid-May misses the first generation. A crop lifted before late August misses the second. Mesh over the row is the method the RHS found most effective, whichever date you sow.