What to do in May

May is a crucial month in the garden as temperatures rise and the risk of frost diminishes. It’s a busy time for planting, sowing and preparing your garden for the growing season ahead:

Things to do in May:

Protect tender plants from late frosts.
Prune spring flowering shrubs and prune clematis Montana after it has flowered.
Trim box and other formal hedging lightly.
Continue taking cuttings from herbaceous perennials.
Plant out dahlias at the end of the month.
Protect young plants from slugs and snails.
Clear out spring bedding for planting summer bedding plants.
Thin out annuals and vegetables sown earlier.
Mow weekly if you prefer a more manicured lawn.
Apply lawn fertilisers now if necessary.
Sow and plant out tender vegetables and continue successional sowing of vegetables.
Remove all frost protection from plants at the end of the month.
Ventilate any greenhouse of conservatories in warmer weather.
Move tender plants outside for the summer.

Last Chance:

Sow or turf new lawns before the conditions become too dry.
Finish planting evergreen shrubs.

Getting Ahead:

Sow biennials for next year’s spring bedding plants.
Inspect plants regularly for signs of pest and disease and nip potentials problems in the bud.

The Weather

May is mild to warm, with average day time temperatures ranging from 14°C to 16°C and night time temperatures between 6°C and 8°C. Frost is unlikely as daytime temperatures start to feel pleasant rising as the month progresses.
Expect moderate rainfall with occasional thunderstorms.
The days are getting longer with more sunshine, though showers can still occur.

Here’s a detailed checklist of what to do in the garden during May, broken down into categories for clarity. May is a busy, exciting month where spring shifts firmly into summer-mode, so many tasks involve planting out, tidying, maintenance, and watching for pests.

General Tasks

Tidy up:	Continue to tidy up the garden, removing any remaining winter debris, fallen leaves, or spent plants. This helps reduce the risk of pests and diseases.
Weeding:	Regularly weed garden beds, borders and paths to prevent weeds from taking over. Weeds grow quickly at this time of year, so stay on top of them.
Watering system check:	Ensure your irrigation or watering systems are in good working order and install or check any new systems before the hotter summer months arrive.

Vegetables & Herbs

Harvesting:	Continue cutting asparagus, early gooseberries should be ready for picking.
Sowing outdoors:	Sow direct-seed vegetables like swedes, turnips, beans, peas and squashes (pumpkins, Courgettes, marrow), cabbage, cauliflower and carrots directly into the soil as the temperature should now be warm enough.
Plant out seedlings:	Once the risk of frost has passed (usually around mid-May), harden off and plant out seedlings of tender vegetables such as tomatoes, Courgettes, cucumbers and peppers that you started indoors.
Protect:	Put netting over particularly brassicas before the birds (pigeons) get to them !
Succession sowing:	To ensure a continuous harvest, start sowing more vegetables for late summer, such as salad leaves, spinach and radishes.
Plant herbs:	Plant out hardy herbs like rosemary, thyme and mint. If you haven’t done so already, sow tender herbs such as basil and coriander in pots or garden beds.

Fruit

Plant strawberries:	May is a great time to plant strawberry runners and crowns for a good crop later in the summer.
Prune fruit trees:	Prune any remaining fruit trees, particularly apples and pears, to shape them and remove any weak or damaged growth. Avoid cutting too much, as fruit trees should not be pruned heavily while in active growth.
Support fruit crops:	Install supports, such as stakes or cages, for tall or vining fruit crops like peas, beans and blackberries.
Mulch fruit trees:	Apply mulch around fruit trees and bushes to retain moisture and suppress weeds.

The Flower Garden

Support tall plants:	For tall-growing plants like delphiniums, hollyhocks and peonies, set up stakes or supports to keep them upright as they grow.
Plant summer bedding:	This is the prime time to plant summer bedding plants such as petunias, begonias and marigolds in borders and containers.
Deadhead spring flowers:	Deadhead spring flowers like tulips, daffodils and hyacinths to prevent seed formation and encourage stronger growth for next year.
Sow annual flowers:	Continue sowing hardy annuals, such as sunflowers, cosmos and cornflowers, directly in the garden or in pots for later transplanting.
Plant summer-flowering bulbs:	If you haven’t done so already, plant summer-flowering bulbs like lilies, gladiolus and dahlias for vibrant late-season flowers.

The Greenhouse

Sow more seeds:	Continue sowing seeds for crops like lettuce, leeks and carrots in pots or trays for transplanting outdoors later.
Planting:	Plant out heat-loving crops such as tomatoes, cucumbers, peppers and aubergines in the greenhouse. Ensure the temperature is consistently warm.
Hardening off:	Start hardening off any indoor-grown plants by gradually acclimatising them to outdoor conditions over the course of a week or so, before planting them in the garden.
Ventilation:	As temperatures rise, regularly ventilate the greenhouse to prevent overheating and encourage good airflow.

Containers

Plant containers:	Fill containers with summer plants like fuchsias, geraniums, begonias and sweet peas for vibrant colour. Choose varieties that suit your container size and growing conditions.
Check drainage:	Ensure containers have good drainage to prevent waterlogging and refresh the compost if needed to encourage strong plant growth.
Water regularly:	As the weather warms, keep containers well-watered, especially during dry spells, as they can dry out more quickly than plants in the ground.

Trees & Shrubs

Planting:	May is a great time to plant trees and shrubs, particularly container-grown varieties, as the soil is warming up and they can establish well.
Prune spring-flowering shrubs:	Prune spring-flowering shrubs like lilacs and camellias after flowering, to shape them and remove spent flowers.
Feeding:	Apply a slow-release fertiliser around established trees and shrubs to support their growth during the active growing season.
Pests:	Look for signs of pests, such as aphids or caterpillars and treat plants if necessary. Early action can prevent more significant infestations.

Hedges

Trim hedges:	Now that growth has started, you can trim hedges for shape and maintain their health. This includes trimming boxwood, privet and other deciduous or evergreen hedges.
Feed hedges:	Apply a general-purpose fertiliser around the base of hedges to encourage healthy growth during the growing season.

The Lawn

Repair bare patches:	Patch up any bare spots in the lawn with fresh grass seed or turf, making sure the ground is prepared and moist.
Mowing:	Mow the lawn regularly to maintain a tidy appearance. Avoid cutting more than a third of the grass height at once to avoid stressing the grass.
Feeding:	Apply a spring lawn feed to promote healthy growth, especially if you haven’t already done so in the early part of the year.
Aerating:	If the soil is compacted, aerate your lawn to allow water, air and nutrients to reach the roots.

Wildlife and the Pond

Clear debris:	Remove any fallen leaves, debris or dead plant material from the pond to maintain water quality and reduce algae growth.
Check water levels:	As the weather warms, monitor the water levels in the pond and top up if necessary.
Add plants:	Plant oxygenators and marginal plants like water lilies, irises and marsh marigolds to support aquatic life and help keep the pond water clean.
Wildlife:	Check the pond for signs of life, like frogs, newts and aquatic insects, which may begin emerging as the temperatures rise. Make sure there are no obstructions that could harm wildlife.

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