climate timing
May garden tasks UK — complete sow, plant and watch list
Your complete UK May gardening guide — what to sow, plant out, watch for and harvest now, with regional timing for the south coast, Midlands and Scotland.
May garden tasks UK — complete sow, plant and watch list
May is the most decisive month in the British gardening year. Pick the right week to plant out tomatoes and you gain a month at the back end of the season; pick the wrong one and a single clear night below 2°C kills a tray of carefully raised seedlings. This guide is the regional UK calendar — what to sow, plant, watch and harvest — broken down by the south coast, the Midlands and Scotland, with the RHS-aligned timing that experienced gardeners use to override the chart in any given year. It is part of the rolling monthly series — once May is done, move on to the June garden tasks, and use the frost date calculator to localise every date to your postcode. The full series lives in the garden calendar hub.
Postcode-specific reminders: Add your postcode to Growli and the app ties every May reminder to your specific area's last-frost date and the live Met Office forecast — so a cold May pushes your tomato transplant date a fortnight later than the chart says.
May climate snapshot — the three UK regions
The UK is not one growing zone in May. The difference between the Lizard Peninsula and the Cairngorms is roughly four growing weeks — which means a chart-based "plant tomatoes in May" instruction is meaningless without a regional split.
| Region | Average last frost | Soil temp at 10 cm (mid-May) | Plant-out window for tomatoes |
|---|---|---|---|
| South coast, Cornwall, Channel Islands | Mid-April | 12-14°C | Early to mid-May |
| Southern England, Wales, East Anglia | Late April | 11-13°C | Mid- to late May |
| Midlands, northern England | Early to mid-May | 9-11°C | Late May to early June |
| Scotland, Northern Ireland | Mid- to late May | 8-10°C | Early to mid-June |
Frost-date averages are statistical. The Met Office notes that late cold snaps from Scandinavian or Russian air masses remain a threat through to May across most of the UK — so the chart date is the earliest reasonable target, not a green light. Always check the 7-10 day forecast before committing tender seedlings to open ground.
For a sharper estimate, look up your specific postcode hardiness rating or use the frost date calculator.
Sow indoors and harden off
If you have not already sown the tender crops indoors, you are running late — but early May is still a workable starting window in Scotland and northern England.
Still sow indoors in early May:
- Tomatoes, peppers, aubergines — only for short-season varieties (Glacier, Tumbling Tom). See when to plant tomatoes in the UK for the full counting-back schedule.
- Courgettes, marrows, pumpkins, squash — sow into 9 cm pots in a heated propagator at 18-21°C. Two weeks indoors then plant out at end of month.
- French beans, runner beans — sow into deep modules; plant out at the end of May once frost risk passes.
- Sweetcorn — sow into deep modules indoors. Sweetcorn hates root disturbance, so use root-trainers or biodegradable pots.
- Basil — sow on a warm windowsill; basil refuses to germinate below 18°C.
Harden off everything raised indoors for at least seven days before planting out — set seedlings outside in a sheltered, shady spot for an hour on day one, building up to a full day by day seven. Skipping harden-off shocks the plants and sets them back two to three weeks. The full sequence is in our seed starting indoors UK guide.
Sow outdoors — direct into the ground
Once soil at 10 cm depth holds steady at 8°C overnight, you can direct-sow the cool-season crops. A soil thermometer pushed into the bed first thing in the morning is the only reliable check.
Vegetables to direct-sow in May:
- Beetroot — sow in drills 2 cm deep, thin to 10 cm. Pull as baby beets from late June.
- Carrots — sow Nantes or Amsterdam Forcing for early crops. Cover with fleece against carrot fly.
- Lettuce, rocket, salad leaves — sow short rows every two weeks for continuous picking. Heat-tolerant varieties (Cervanek, Little Gem) bolt slower in June.
- Peas — main-crop varieties (Hurst Greenshaft, Kelvedon Wonder) for July picking; support with twiggy pea sticks.
- Radishes — French Breakfast and Cherry Belle crop in 4-5 weeks.
- Spring onions, chives — sow in short rows for summer salad.
- Parsnips — sow direct into warm soil; germination is slow (3-4 weeks).
- Spinach, chard — sow now for June picking. Chard tolerates heat better than spinach.
- Turnips — fast-growing for June pulling (Snowball, Atlantic).
- French beans (late May) — direct-sow once soil is 12°C+. Cover with cloches for the first ten days in the Midlands.
Herbs to direct-sow:
- Coriander — sow short rows every fortnight; it bolts in heat.
- Dill — direct-sow into warm soil; it hates transplanting.
- Parsley — slow to germinate (3-4 weeks); soak seeds overnight first.
The RHS notes that this is also "the perfect time to sow winter brassicas" (cabbage, kale, sprouting broccoli) for transplanting in July — sown earlier and the greens overwhelm beds still occupied by spring crops.
Plant out — the tender crops
Once your local last-frost date has passed and the 10-day forecast shows no nights below 5°C, the floodgates open:
Vegetable transplants:
- Tomatoes — outdoors in southern England from 15 May, the Midlands from end of May, Scotland from early June. Greenhouses run 2-3 weeks earlier. Stake or cage at transplant — never after.
- Peppers, aubergines, chillies — into the greenhouse or polytunnel only across most of the UK; outdoors restricted to Cornwall, the Channel Islands and warm walled gardens in the south.
- Courgettes, marrows, squash — plant out end of May once frost is past. Allow 90 cm spacing.
- Sweetcorn — plant in blocks of 16+ plants (4×4 minimum) for wind pollination, never in single rows.
Ornamentals — the big one is dahlias:
- Dahlias — plant out tubers after the last frost (late May in the south, early June further north). Stake at planting. A single late frost blackens the foliage and sets the plant back a fortnight.
- Bedding plants — petunias, geraniums, busy lizzies, begonias from late May. Wickes, B&Q, Crocus and Sarah Raven all stock plug plants by mail or in branch.
- Sweet peas — autumn-sown sweet peas should be in the ground; spring-sown go out now and will flower from late July.
- Cannas, hedychiums — plant out late May once nights stay above 10°C.
The RHS recommends the Chelsea chop on summer-flowering perennials in late May — cut back the new growth on hylotelephium, nepeta, phlox and Michaelmas daisies by about a third to encourage stouter, more wind-resistant plants and a longer flowering window.
Maintain — pruning, feeding and watering
May is when growth accelerates and weekly maintenance becomes worth doing:
- Mow the lawn weekly at around 4 cm; raise the blade for the first cut after April.
- Feed established lawns with a spring lawn feed (high nitrogen). Wait until the next forecast rain or water in within 48 hours.
- Prune spring-flowering shrubs — forsythia, ribes, kerria and chaenomeles can be cut back as the flowers fade.
- Tie in climbing roses and clematis — new shoots are soft and will snap in May winds without horizontal support.
- Stake tall perennials (delphiniums, peonies) before they fall.
- Feed flowering shrubs with a balanced granular feed (Growmore or fish-blood-and-bone) around the drip line.
- Pinch broad beans — once the first 4-5 flower trusses have formed, pinch out the growing tip to redirect energy and discourage blackfly.
Water any newly planted shrubs, trees and perennials deeply at planting, then weekly through May if rain is sparse. Container plants need daily checks once temperatures top 18°C.
Pest and disease watch — UK-specific
May is peak pest pressure as overwintered slugs, snails and aphids find tender new growth.
- Slugs and snails — the single biggest UK May problem. Hostas, dahlias, lettuce, brassicas and beans are all targets. Beer traps, copper rings, nematode drench (Phasmarhabditis hermaphrodita, sold as Nemaslug) or torch-and-tweezer night patrols all work. The RHS's evidence-based hierarchy puts cultural methods first.
- Aphids on roses and broad beans — black bean aphid colonies appear on broad bean tips in mid-May. Pinch the tip out and squash any colonies; the populations crash naturally once ladybirds and hoverflies move in. Resist insecticides — they kill the predators that solve the problem.
- Carrot fly — adults emerge in May. Cover carrot rows with horticultural fleece or insect mesh from sowing.
- Lily beetle — bright red adults appear on lilies and fritillaries. Hand-pick daily.
- Asparagus beetle — emerges in May; hand-pick on warm afternoons.
- Late frost — clear, still nights below 4°C in late May still happen across the Midlands and north. Cover tender transplants with fleece if a frost is forecast.
For diagnostic walkthroughs of the most common UK pest problems, see aphids on plants and our what's wrong with my plant troubleshooter.
Harvest now
By mid-May, the spring crops sown in February and March are ready to crop:
- Asparagus — peak month. Cut 18-22 cm spears at soil level with a sharp knife. Stop cutting on 21 June to let the fern build up the crown for next year.
- Rhubarb — pull (don't cut) tender pink stems through May and June. Stop pulling in late June.
- Spring greens, spring cabbage — heading up from autumn sowings.
- Lettuce, rocket, mustard greens — the first cut-and-come-again pickings from April sowings.
- Radishes — fastest crop in the garden, ready 4-5 weeks from sowing.
- Spring onions — pull from April sowings.
- First strawberries — under cloches in Cornwall and south coast gardens.
- Herbs — chives are at peak flavour; mint is exploding (keep contained or it takes over).
Order for next month
May is when forward planning pays. Order now for June planting and beyond:
- Strawberry runners for July planting (Sarah Raven, Marshalls, Suttons, D.T. Brown).
- Autumn-fruiting raspberry canes for next-month planting (autumn delivery is the better window, but May orders secure stock).
- Leek plants — order plug plants from D.T. Brown or Marshalls for June transplanting; the only way to crop leeks if you missed the February sowing.
- Brassica plug plants for July transplanting — Brussels sprouts, sprouting broccoli, winter cabbages. Crocus and Suttons both post.
Quick wins — five-minute May tasks
The compounding wins this month:
- Net strawberry beds against birds the first week the flowers open. Birds know before you do.
- Pinch out broad bean tops the moment the first pods set.
- Snap suckers off cordon tomatoes the same day they appear — by week three a missed sucker is a second main stem.
- Top up bird-baths daily in dry weather. Fledgling season runs through May.
- Refresh slug-trap beer twice a week — stale beer attracts more slugs than fresh.
- Plant a row of dwarf French beans every fortnight for succession through August.
Related articles
- When to plant tomatoes in the UK — the full regional timing chart
- Seed starting indoors UK — for tender crop sowings
- June garden tasks UK — what comes next
- Aphids on plants — UK guide — for the peak May aphid window
- UK RHS hardiness ratings explained — find your specific area's rating
- Frost date calculator — pinpoint your last-frost date
Reviewed and updated by the Growli editorial team. For questions about anything here, open Growli and ask — or email hello@getgrowli.app.
Frequently asked questions
What can I plant in May in the UK?
In May you can plant out tomatoes, courgettes, marrows, squash, French beans, runner beans, sweetcorn, peppers (under cover), aubergines and basil after the last frost. Direct-sow lettuce, radishes, beetroot, carrots, peas, spring onions, parsnips, chard, spinach and turnips. Plant out dahlia tubers, bedding plants, sweet peas and cannas. Sow winter brassicas (cabbage, kale, sprouting broccoli) for summer transplanting.
When is it safe to plant out tomatoes in the UK in May?
Mid-May in southern England and Wales, late May in the Midlands and northern England, early June in Scotland and Northern Ireland. The RHS rule is to wait until night-time temperatures have stopped dipping below around 7°C. Always check the Met Office 10-day forecast before committing tender plants — a single clear May night below 2°C will kill seedlings. In Cornwall and the Channel Islands you can plant from early May.
Can I sow seeds outside in May UK?
Yes — most of the cool-season vegetables sow directly into warm May soil. Carrots, beetroot, lettuce, radishes, peas, parsnips, chard, spinach, turnips and spring onions all germinate well from May sowings. From mid- to late May (once soil is 12°C+) you can also direct-sow French beans, runner beans, courgettes and sweetcorn. Soil temperature at 10 cm depth is more reliable than air temperature — buy an inexpensive soil thermometer.
What should I be doing in my garden in May UK?
May tasks split into five jobs: (1) plant out tender crops raised indoors after frost risk passes, (2) direct-sow cool-season vegetables into warm soil, (3) harden off everything before transplanting, (4) watch for slugs, aphids and late frost, and (5) feed and stake fast-growing perennials. Mow the lawn weekly, pinch broad bean tops once pods set, and net strawberries against birds. Order brassica plug plants and strawberry runners for June.
When is the last frost in the UK in May?
South coast and Cornwall: mid-April average; southern England and Wales: late April; Midlands and northern England: early to mid-May; Scotland and Northern Ireland: mid- to late May. The Met Office notes that late cold snaps from Scandinavian or Russian air masses remain a threat through May across most of the UK. Cornwall, south Devon and the Channel Islands are typically frost-free by mid-April; the Scottish highlands can see frost into early June.
Should I plant dahlias in May in the UK?
Yes — plant dahlia tubers outdoors after your last frost, which means late May for the south and early June for the Midlands and north. Stake at planting (driving a cane in afterwards risks spearing the tuber). A single late frost will blacken the foliage and set the plant back a fortnight, so cover with fleece on cold clear nights. In Cornwall and the Channel Islands you can plant from late April.
How do I deal with slugs in May UK?
Slugs are at peak pressure in May — overwintered adults find tender new growth. Use the RHS evidence-based hierarchy: cultural methods first (clear hiding places, water in the morning not evening), physical barriers (copper rings, sharp grit), beer traps refreshed twice a week, then biological control (Nemaslug, a nematode drench applied in March, April and May). Avoid metaldehyde slug pellets — they were banned in the UK in 2022. Ferric phosphate pellets are the legal chemical option.
How does Growli decide when to plant tender crops in my UK postcode in May?
Add your postcode to Growli and the app ties every May planting reminder to your specific last-frost date from Met Office historical data plus the live 10-day forecast. The reminder only fires when night temperatures are reliably above 7°C and the 10-day outlook shows no frost. A cold May pushes your tomato and dahlia planting reminder a fortnight later than the chart says — so you do not lose seedlings to a Bank Holiday cold snap.