Month by month
Garden jobs for May: planting out and the Chelsea chop
May is one of the loveliest months in the garden, with fresh green growth, blossom and the first flush of early summer flowers. It is also one of the trickiest. Late frosts are common in the first half of the month across much of the UK and Ireland, and later still in Scotland, northern England and frost pockets. A good working rule is to wait until late May before planting out tender plants in the north, and mid-May in the mild south and west. Long dry spells are also likely, so water anything newly planted. Weeds grow as fast as everything else; hoe on dry days and they will wither in the sun.
Flowers and borders
Try the Chelsea chop in the last week of the month, named after the famous flower show held at that time. Cut back clumps of late-summer perennials such as sedum, phlox, rudbeckia, echinacea and Michaelmas daisies by a third to a half. They flower a little later, on shorter, sturdier stems that rarely need staking. For a longer display, chop only the front half of each clump.
Harden off bedding plants and tender perennials for a week or two by putting them out during the day and bringing them in at night. Plant out dahlias, cosmos and other frost-tender plants only when frosts are over in your area. Sow nasturtiums and sunflowers outdoors in sunny spots.
Lift and divide clumps of spring bulbs that flowered poorly, once their leaves have yellowed. Clip box hedges and topiary late in the month, but check for box tree caterpillar first: look for webbing and green-and-black caterpillars inside the plant and pick them off. Tie in climbers such as clematis and honeysuckle as they grow, and prune spring-flowering clematis montana after flowering if it has outgrown its space.
Vegetables
Sow runner and French beans, courgettes, squashes, pumpkins and sweetcorn directly outdoors from mid-May in the south and late May further north, or plant out those raised in pots after hardening them off. Sweetcorn is pollinated by wind, so plant it in blocks rather than single rows.
Carry on sowing salads, beetroot, carrots and peas in succession. Thin earlier sowings to their final spacing; thinned lettuce and beetroot leaves make good salad. Earth up potatoes as they grow, and keep fleece handy for frosty nights. Plant out leeks, brassicas and celery, and protect brassicas from cabbage white butterflies and pigeons with fine netting.
Fruit
Tuck straw or mats beneath strawberry plants to keep fruit off the soil, and net them against birds. Water fruit trees and bushes in containers regularly, and feed with a high-potash fertiliser once flowering finishes. Thin gooseberries late in the month, using the thinnings for cooking. Train in the new canes of blackberries and hybrid berries, and check apples and pears for aphids, sawfly and other pests; a firm squeeze or a jet of water deals with most small colonies.
Lawns
Mow at least once a week, and consider leaving part of the lawn unmown for the month. Even a small patch lets dandelions, clover, self-heal and buttercups flower for pollinators, and you may be surprised by what appears. Feed the rest if you did not in April, and water newly sown grass in dry weather. Trim lawn edges after each cut for a neat finish.
Wildlife
May is peak nesting season, so leave hedges and climbers alone unless you are certain they are empty. Pollinators are out in force; plant a range of flowers to keep the supply going. Catmint, salvia nemorosa, alliums and open-flowered herbs such as chives are all bee magnets. Avoid spraying pesticides, as ladybirds, lacewings and birds will control many aphids if you give them a chance.
Indoors and under cover
Plant greenhouse tomatoes, cucumbers, peppers and aubergines into their final pots or growing bags. Pinch out the side shoots on cordon tomatoes, start tying them to canes or strings, and water regularly. Shade the glass and damp down the floor on hot days to keep humidity up and red spider mite away. Sow biennials such as foxgloves, wallflowers and sweet Williams in a seedbed or pots for flowering next year.
Plants looking good this month
May is full of colour and scent:
- Alliums hold up purple globes above the borders.
- Wisteria drapes walls and pergolas with hanging racemes.
- Lupins send up tall spires in every colour.
- Aquilegia self-seeds and flowers through borders.
- Ceanothus turns walls a vivid blue.
- Rhododendrons and azaleas are in full bloom in acid soils.
- Oriental poppies open papery flowers late in the month.
- English bluebells carpet shady areas.
Catch up with April jobs or move on to June jobs.
From the plant finder
In flower in May
Good time to plant
Due for pruning
Grow your own in May
Sow now
Plant out
Ready to harvest
Problems to watch for in May
Spotted something else? Diagnose it by symptom.
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