May in the garden

May has arrived and the days are getting warmer and longer. Summer is on its way and it’s time to tidy up spring plants, plant out summer flowers and get planning for autumn.

 

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Flowers

Prune spring shrubs, such as forsythia and chaenomeles, after flowering to keep them compact
Plant out dahlia tubers and cannas after all risk of frost has passed
Tie in the new shoots of climbing plants, including clematis, wisteria and honeysuckle, to their supports
Continue sowing annuals, such as California poppies, into gaps in borders for colour from August into autumn
Plant up hanging baskets, but keep in a greenhouse or porch for a few weeks to establish, before putting outside
Apply liquid feed to tulips, daffodils and other spring bulbs to encourage a good display next year
Plant out summer bedding and tender annuals, including sunflowers, cosmos and nasturtiums, after the last frost
Remove faded spring bedding, such as wallflowers and forget-me-nots, once faded and add to your compost bin
Check lilies and fritillaries for scarlet lily beetles and their larvae, as they can rapidly strip plants of all foliage
Harden off tender plants raised indoors, but bring them back in at night to protect from late frosts
Pinch out the shoot tips of bedding plants and young annuals to encourage bushier growth
Add interest to shady borders by planting a selection of hostas and ferns

 

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Fruit and veg

Earth up potatoes, covering the shoots with soil as they appear
Sow sweetcorn in deep pots, so the young plants are ready to transplant into the garden in June 
Reduce snail populations by going on regular evening hunts, especially during damp weather
Start sowing dwarf and climbing French beans, as well as runner beans, directly outdoors in warm weather
Pick rhubarb stems as they develop, and water plants with liquid feed
Start hardening off tender young plants, such as tomatoes and courgettes, ready for planting out in mild areas
Sow batches of salad leaves and stir-fry crops every few weeks to provide continuous pickings
Hang pheromone traps in apple and plum trees from May to July, to control pests
Thin out seedlings from earlier sowings to ensure you get healthy, strong-growing plants
Open fruit cage doors or lift some of the netting to ensure pollinating insects can get access to the flowers
Remove all strawberry runners, so plants put their full energy into fruiting
Keep plenty of fleece handy to protect young seedlings or fruit blossom, if late frosts are forecast
Sow radishes in gaps for an extra crop

 

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Greenhouse

Water thirsty crops such as tomatoes, cucumbers and courgettes regularly as the weather starts to warm up
Tie the stems of indoor tomatoes, cucumbers and aubergines to canes as they grow
Plant heat-treated freesia corms in pots for fragrant flowers this summer
Check plants regularly for pests, on shoot tips and the underside of leaves, and treat with biological controls
Put up shading to lower daytime temperatures and reduce scorching
Open doors and vents on warm days, but close them in the evening as nights can still be cold
Take cuttings of woody herbs such as hyssop, rosemary and thyme, and root in pots of gritty compost
Keep pricking out seedlings as soon as they get their first true leaves, to avoid overcrowding and fungal diseases
Repot any houseplants that have become top heavy or pot bound into larger containers
Start to harden off tender plants and bedding, ready for planting outside after the last frost
Take cuttings from fuchsias, dahlias and pelargoniums
Transplant tomatoes into growing bags or large pots, and tie their main stem to a cane or vertical wire for support


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Garden maintenance

Scoop out pondweed, blanketweed and algae from ponds and water features
Put soft tops on the tips of all canes, in borders, veg plots, pots and greenhouses, to prevent injury to eyes
Apply wood treatment to wooden garden furniture to condition it for summer
Set up an extra compost bin or a worm bin, so you can recycle more green waste from your kitchen and garden
Apply nitrogen-rich summer lawn feed to encourage leafy growth
Mow grass pathways through wildflower areas so you can walk in among the flowers 
Hoe bare soil and hand-weed beds weekly, so weeds don't have time to establish and set seed
Put supports in place for clumps of perennials that are prone to flopping, such as top-heavy peonies or phlox
Trim topiary regularly to promote bushy growth and keep it looking neat
Sow grass seed or lay new turf by the end of this month, to create a new lawn or repair damaged patches
Check shrubs for nests before you start any pruning, to avoid disturbing nesting birds
Clean out and scrub bird feeders regularly to maintain hygiene
Build sturdy wigwams and supports for climbers such as runner beans, sweet peas and morning glory

 

Source: BBC Gardeners' World