Weekend Work: Time to sow lettuce and radish seeds Lettuce and radish are best eaten young, so seed should be sown a little at a time at monthly intervals. I've adopted the trick used by a professional-gardener friend . He sorts his seed packets in a tin, in the order he wants to sow them. Card dividers separate each month. When lettuce has been sown in May, he puts the seed packet back in the box to be used again in June. Start off courgettes in small pots inside. Sow seeds two to a pot and wrap in plastic film until the seedlings emerge. A few young tomato plants can be risked outside in mild areas. Cut off any raspberry suckers coming through more than 15cm (6in) from the original row. Pinch out the tops of rooted cuttings of geranium and fuchsia. Plant out sweet peas raised in pots. They will need something to scramble up, either plastic mesh, sticks, or bamboo canes. Try to keep on top of the most free-seeding weeds. In my garden, groundsel, landcress and dandelion are the worst offenders. What to buy An exhibition celebrating art in the garden opens today at Avebury Manor, Wiltshire. It features work by more than 20 contemporary sculptors, set against the gardens' formal topiary, orchard and herbaceous borders. All works are for sale. Open daily (11am-5pm) until 10 June; for more details call 01672 539250.