May is a busy month, as bedding plants are planted out, tall border perennials will need staking and the schedule of jobs including watering, weeding and mowing becomes more regular.
But the weather can still be changeable, so if a late frost is predicted, make sure you protect your tender plants with horticultural fleece. And watch out for pests, dealing with them before they infest your plants.
What to do with your flowers
- Plant dahlia bulbs towards the end of the month, inserting a stake next to each planting hole and protect young plants from slugs.
- Pinch out the growing tips of bush fuchsias while the plants are still small and check all types of tender fuchsias for pests, as they are particularly vulnerable now.
- Continue to harden off tender bedding and if you plant it out this month, protect it with horticultural fleece at night if frost is forecast.
- For a succession of blooms throughout the summer, sow fast-maturing annuals including calendulas, candytuft, godetias and clarkias every two weeks until mid-June.
- Sow late-flowering annuals including nicotianas, ageratums and nasturtiums under glass then prick them out into pots or divided seed trays. They make perfect gap fillers and if sown now will flower from August until the first frosts.
- Prune spring-flowering clematis after flowering, cutting back all last year’s growth on types including C. alpine and C. macropetala to 25-30cm from point of origin.
Hanging baskets and window boxes
- Try to complete the planting of permanent containers by early May so that plants have the long summer ahead to establish themselves.
- Harden off hanging baskets by sitting them in a large pot in a sheltered corner during the day. Return them under cover, whether it be in a greenhouse or under a porch, at night. Don’t put them in windy areas or they can suffer wind damage.
- Spruce up windowboxes, throwing away faded annuals but saving ivies and other evergreens such as euonymus for summer displays in the garden.
- When planting up pots, add slow-release fertiliser and water gel crystals to the compost to give the plants a boost and help keep the soil moist during the warmer months.
Fruit and veg to sort
- Don’t let newly planted fruit bushes and trees run short of water. If it’s windy, a short, sharp downpour may not provide enough water to keep the soil as moist as it needs to be.
- Apple and pear trees planted for less than two years shouldn’t be allowed to carry crops as it will stunt their growth. Limit the potential crop by rubbing out flower clusters or removing fruitlets by hand.
- Harden off aubergines, courgettes, marrows, peppers, pumpkins and tomatoes grown from seed before planting outside.
- Sow French and runner beans and erect supports for climbing beans.
- Cover the ground under strawberries with straw or matting to protect the ripening fruit from mud and from slugs and other pests.
- Repot greenhouse tomatoes which are outgrowing their pot and pinch out sideshoots which can then be treated as cuttings if put into pots of free-draining compost and watered in. Keep them in the greenhouse until they root.
- Sow herbs including basil and parsley every two weeks to give you a continuous supply over summer.
What to do with your lawn
- Continue to scarify the lawn lightly with a spring-tined rake where thatch and dead moss are a continuing problem.
- Weaken patches of coarse grass by regularly cutting out the clump with a knife.
- Start to cut grass more regularly, lowering the blades as required.
- Cut grass containing naturalised bulbs around six weeks later than other grass, to allow the bulb leaves enough time to build up their reserves for flowering next year.
Weed and feed
- Treat large-leaved weeds such as dandelions with a stick touch weeder or dig them out by hand, removing all pieces of tap roots. On lawns, fill holes with compost or sifted soil.
- Feed your spent spring bulbs with sulphate of potash or tomato feed while they are still in leaf, as this will boost next year’s flowers.
- Remove the top layer of compost from permanent containers and replace it with fresh compost mixed with slow-release fertiliser.
- Feed seedlings and young plants which are growing poorly or have pale, yellowing foliage.
- Water and feed plants in the greenhouse regularly.
- Keep on top of weeding in beds and borders, looking out for pernicious perennial weeds such as ground elder and couch grass and trying to remove all their roots before they snap off and re-emerge.