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May is the right month to plant tender varie-ties outdoors, but beware. The Met office predicts cold easterly winds over Britain for at least another week.

What’s more, frost is possible until late May. East wind brings cold air from the North Sea. So even without frost, the chill- factor can bruise tender tissue before the plants have had time to toughen up.

Petunias (right), impatiens, heliotropes and young courgettes are especially vulnerable to frosts.

Do not expose delicate greenhouse or garden centre plants to our fickle weather without first hardening them off which takes a couple of weeks. If you have a coldframe, move plants into that. Leave it uncovered by day, but close it overnight for the first week.

During the second week, leave your frame open unless temperatures are forecast to fall below 5c. after that, the plants will be tough enough for planting out.

If you do not have a coldframe, it’s easy to make a temporary one from cardboard boxes. Remove the tops and place the plants inside, making sure they receive full light. Cover the boxes with horticultural fleece overnight for the first few days, and then only if low temperatures are expected.

fleece is not cheap, but can be reused year after year. Hardening off young varieties like this will delay planting for two weeks. But good summer plants will perform until october or beyond, so it’s well worth doing.