Why are there pale patches on the skins of my glasshouse tomato fruits?

K Chambers, Whitby

This is due to sun scald, and it usually affects greenhouse-grown tomatoes, cucumbers and grapes exposed to strong sunshine. The most obvious sign of damage is slightly depressed, papery and light-brown patches on the fruit; the leaves can be affected in a similar fashion.

To prevent further problems, apply summer-shading paint to the greenhouse glass and keep the structure well ventilated, especially during the heat of the day. It is a good idea to water the tomato plants in the early morning or late afternoon/early evening, as sun scald can be exacerbated when the leaves and fruit are wet.

When is a good time to sow pak choi?

A Langer, Evesham

Pak choi is an oriental salad plant grown for its edible leaves – which are ideal for stir-fries and late-summer salads. It is a quick-maturing crop and can be sown outdoors in July and August. Choose a suitable variety, such as ‘Green Revolution’, and sow the seeds ½in deep in a sunny spot and a fertile, moist but welldrained soil. Once they germinate, thin the young seedlings so they are about 10in apart.

During the growing season, keep the ground damp, especially in dry weather, and protect the pak choi from slugs by surrounding them with circles of coarse grit. You can harvest the mature plants in 6-8 weeks.

Neil Wormald is a qualified horticulturalist. Send your questions to Garden Expert, Home, The Sunday Times, 1 Pennington Street, London E98 1ST, or e-mail garden.expert@sunday-times.co.uk

Our experts cannot send personal replies. Questions may be edited for reasons of space and advice is given without responsibility. Please do not send original documents or SAEs

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