Continue to sow spring cabbage, turnips, Oriental vegetables and overwintering onions, in the south of England.

Irregular watering can lead to problems with blossom end rot in tomatoes, splitting of root vegetables and flower abortion in peas and beans. Help prevent this by watering well during dry spells. We do not advise using grey household water on edible crops, but stored rainwater from a water butt is ideal.

Weeds can also compete with vegetables for water, and act as hosts for pests and diseases, so should be removed regularly by hoeing.

Lift onions, shallots and garlic when ready. Plants should be harvested when the necks start to turn brown and papery, and bend over naturally. Avoid actively bending the necks, as this can result in disease. Once harvested, let the tops dry until they rustle like brown paper, and then remove them.

Regularly pick fast-maturing vegetables such as French beans, runner beans, courgettes, cucumbers and tomatoes, to prevent stringiness or toughness, and to encourage further cropping. Excess pickings can be frozen.

Finish harvesting second early potatoes, especially if it turns wet, as slugs will become active.

Harvest sweetcorn as it ripens. Push a fingernail into the kernel when the tassels at the end of the cob start to shrivel and brown. If the liquid is milky it indicates they are ready.

Marrows should be raised off the ground slightly, to prevent them rotting from contact with the soil. Some older leaves can be removed, if necessary, to maximise sun upon the fruit.

Continue earthing up celery, putting a layer of paper between the stems and the soil.

Take care when thinning out any late-sown carrot seedlings to prevent the scent released attracting carrot fly females. To protect them from carrot fly use fleece or enviromesh coverings.

Sow green manures such as crimson clover and Italian ryegrass to act as a soil improver and to cover bare areas. When dug in, they conserve nutrients and improve soil texture.

Alternatively, after clearing old crops, place black plastic over bare areas of ground to suppress weed growth.

Pest & disease watch

Keep up with potato blight control on outdoor tomatoes and potatoes to prevent further infection of the crop. Cut off the haulms (tops) of blighted potatoes and burn them, or put them in the dustbin. The tubers can still be harvested.

Potato powdery scab is also prevalent at this time of year.

Watch tomatoes for blossom end rot, ghost spot, blotchy ripening and greenback. Problems with ripening can be caused by heat damage, lack of feeding or water, or by a genetic tendency in some varieties. Tomato viruses are another problem.

Look out for the caterpillars and excrement of the pea moth, and for fungal spots on bean and pea pods and leaves.

Remove any sweetcorn cobs affected by smut, with swollen, grey or brown kernels that burst to release powdery fungal spores.

Carrot fly is still about.

Check stored onions for softness and the grey or black mould of neck rot.

Onion eelworm can cause swelling and distortion of onion plants, and rotting of stored bulbs. Crop rotation is the best preventative.

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