Key takeaways
- Plant out tender crops once the frosts are over, usually mid to late May in the south
- Sow runner beans, French beans and sweetcorn outdoors from late May
- Keep sowing lettuce, radish and beetroot every 2-3 weeks
- Earth up potatoes when the shoots are 15-20cm tall
- Harden off indoor-raised plants for 10-14 days before they go out
May is when it all comes together in UK gardens. All that indoor sowing and patient watering pays off as tender crops finally head outside.
Frost is the thing to watch. The Met Office says the last air frost in southern and coastal areas usually comes before the end of April. Further north and on high ground, it can carry on well into May, and in a few places into June. Ground frosts are common in May and still hurt tender plants. So in the south, plant tender crops out from mid to late May. In the north, wait until late May or early June. After that, the garden fills up fast.
This guide covers what to sow and plant in May. It follows our April planting guide and leads on to what to plant in June.
Planting out tender crops
The big May job is moving your indoor-raised plants outside. Everything you sowed in March and April is ready to go.
Hardening off
Before planting out, every indoor plant needs hardening off, which means getting it used to outdoor life bit by bit over 10-14 days. Put them out for a few hours on day one and a bit longer each day after. Bring them in at night for the first week. By day 10, leave them out overnight if no frost is forecast.
Skip this and the plants get a shock. Leaves scorch and they can stop growing for weeks. A warm windowsill to a cold May night is a big jump. Our guide on how to sow seeds indoors covers hardening off in full.
Hardening off seedlings in May. Give them a little more time outside each day for 10-14 days.
Tomatoes
Plant tomatoes outside from the second half of May in southern England. In an unheated greenhouse they can usually go in from early May. Space them 45cm apart in rich soil, and push a strong cane in beside each one when you plant. Tomatoes are hungry, so add a handful of blood, fish and bone to each hole. For timing by region, see our guide on when to plant tomatoes.
Outdoor tomatoes go out from the second half of May in the south. Space them 45cm apart and push in a cane at planting time.
Courgettes and squash
Courgettes are wonderfully productive, and two or three plants feed most families. Plant them 90cm apart in soil with plenty of compost dug in. Water at the base, not over the leaves, to help keep powdery mildew away.
Squash and pumpkins need even more room, about 1.5m between plants. Train the vines outwards. Feed and water them well and they’ll reward you.
Is it too late to sow tomatoes and courgettes in May?
For courgettes, no. Courgettes, marrows and squash can be sown straight outside from late May into early June, under a cloche or jam jar at first. They catch up fast, as they never have to cope with being moved.
Tomatoes are different. Sown in May, they flower late and may only ripen a few fruit before autumn, especially outdoors in the north. A quick bush or cherry variety can work in a greenhouse in the south. For a proper crop, buy young plants instead. The same goes for peppers, chillies and aubergines, which need a long season.
Peppers, chillies, and aubergines
These heat-lovers do best in a greenhouse or against a sunny south-facing wall. Plant them out from late May in your warmest, most sheltered spot. In northern England and Scotland, a greenhouse is the safer bet.
Cucumbers
Outdoor ridge cucumbers go out in late May. Greenhouse types can go in from mid-May in a heated greenhouse. Both like rich soil that stays moist. Water regularly and feed with a tomato feed once the fruit starts to form.
Gardener’s tip: Slip a slate or tile under each courgette, squash and cucumber as it grows. It keeps the fruit off damp soil, which means less rot and fewer slug nibbles.
Outdoor vegetable sowings
May is the month to sow frost-tender crops straight outside, and the last chance for some first sowings.
Runner beans and French beans
From late May, sow runner beans and French beans straight outside. Runner beans climb 2-3m, so put up a wigwam or double row of 2.4m canes before you sow. Sow two seeds at the foot of each cane, 5cm deep, and pull out the weaker seedling.
French beans are shorter and come as bush or climbing types. Bush ones like Tendergreen don’t need support. Sow 5cm deep, 15cm apart in rows 45cm apart.
Runner beans at the foot of a cane wigwam in late May. They’ll twine their own way up.
Sweetcorn
Sow sweetcorn straight outside from late May in the south, ideally under cloches or fleece at first. Grow it in a block of at least 12 plants, not a single row. The wind pollinates it, and a block gives you better-filled cobs. Sow two seeds per spot, 4cm deep and 35cm apart, and pull out the weaker one.
Successional sowings
Keep sowing these every 2-3 weeks for a steady supply:
| Crop | Sow depth | Spacing | Ready in |
|---|---|---|---|
| Lettuce | 1cm | 25cm | 4-8 weeks |
| Radish | 1cm | 3cm | 4-6 weeks |
| Beetroot | 3cm | 10cm | 8-12 weeks |
| Spring onions | 1cm | 1cm | 8-10 weeks |
| Carrots | 1cm | 5cm | 10-16 weeks |
| Spinach | 2cm | 15cm | 6-8 weeks |
Late sowings
Peas can still go in during May and June. Late peas flower in the heat of summer, when dry soil and mildew can cut the crop, so pick a quick variety like Kelvedon Wonder.
Sow turnips and swede now for autumn and winter. They’re both in the cabbage family and like cooler weather, so they fatten up nicely in autumn.
What can you sow in May for winter harvests?
May is the month to sow the winter brassicas (the cabbage family). Kale, purple sprouting broccoli, winter cabbage and cauliflower can all go into a seedbed or modules now. Move them to their final spot in June or July once spring crops are cleared. Swede sown now stands in the ground well into winter.
Leeks sown in March and April can be planted out from late May into June. Make a 15cm deep hole with a dibber, drop in a seedling and fill the hole with water, not soil. Net young brassicas against pigeons and cabbage white butterflies as soon as they go out.
Watch out: Flea beetles love newly sown turnips and radish. These tiny black beetles leave little round holes in the leaves. Cover seedlings with fleece straight after sowing. Bigger plants shrug off a few holes.
Drop each leek seedling into a 15cm dibber hole and fill it with water, not soil. The soil settles round them naturally as they grow.
Potatoes
Earthing up
Earth up all your potatoes in May. When the shoots are 15-20cm tall, pull soil up around the stems until only the top few centimetres show. This keeps the new potatoes in the dark, as green potatoes aren’t safe to eat.
Do it again when the leaves push through. By the end of May you should have neat ridges along each row. Our potato growing guide has the whole process.
Watering
Potatoes like steady moisture, especially once they flower, as that’s when the potatoes are forming. Give them a deep soak once or twice a week rather than a little every day. Deep watering sends the roots down, so they cope better in dry spells.
Flowers to sow and plant in May
May is when the borders fill with colour as summer bedding goes out.
Summer bedding
After the last frost, plant out summer bedding: petunias, begonias, geraniums (pelargoniums), lobelia, impatiens and marigolds. They’ve been raised in warmth and can’t take frost, so wait until you’re sure it’s safe.
Direct sow outdoors
- Sunflowers: sow where they’ll grow, 2cm deep. Giants like Russian Giant can top 3m, while dwarf Sunspot stays around 60cm. For timing, see our sunflower planting guide.
- Nasturtiums: push the big seeds 2cm into the soil. They flower best in poor soil, and are often grown near veg to lure blackfly away.
- Marigolds (French and African): sow 1cm deep, or plant out ready-grown plants.
- Night-scented stock: scatter the seed near a bench for lovely evening scent.
Dahlias
Plant dahlia tubers outside in May, or plant out pot-started dahlias once the frosts are over. Give them a sunny, sheltered spot and rich soil. Set the tubers with the shoots facing up, under about 10cm of soil, and 45-60cm apart. Put stakes in for tall ones at planting time, so you don’t spear the tubers later. Protect young shoots from slugs, which can strip them overnight.
Hanging baskets
Plant up hanging baskets in mid-May, ready to hang out after the last frost. Mix trailing plants (lobelia, petunia, bacopa) with upright ones (geraniums, fuchsia). Water them daily in warm weather. By midsummer they may need it twice a day.
Planting up hanging baskets in May. Keep them under cover until the last frost has passed.
Perennials
May is a great month to plant hardy perennials from the garden centre. The soil is warm, there’s usually some rain, and plants settle in fast. For north-facing borders, our guide to the best plants for shade has reliable picks.
Herbs
Plant out
Move herb seedlings raised indoors to their final spots from mid-May. Basil wants the warmest spot in the garden, or a greenhouse. Parsley, coriander and dill are happy in any well-drained bed.
Direct sow
Sow basil outside from late May in a sheltered, sunny spot. French tarragon, lemon balm and mint are easier bought as plants than grown from seed.
Harvesting
Start picking established herbs like chives, mint and oregano from May. Regular snipping keeps them bushy. Don’t take more than a third of a plant at once.
Fruit
Strawberries
Strawberry plants flower in May. Tuck straw or fibre mats around them to keep the fruit clean and dry. Net them too, as birds are quick to spot ripe berries. Our strawberry guide has the full story.
Fruit trees
Have a look at your apple and pear fruitlets in late May, but don’t thin yet. Wait for the “June drop”, when trees shed extra fruit on their own. Then thin heavy crops from mid-June to July. Take off the smallest and any damaged ones, leaving one or two per cluster about 10-15cm apart.
Soft fruit
Feed soft fruit (currants, gooseberries, raspberries) with a high-potash feed in May. Mulch with compost to keep the soil moist through summer. Check gooseberries for sawfly caterpillars, which can strip a bush in days, and pick them off.
May planting calendar
| Week | Indoors | Outdoors | Plant out |
|---|---|---|---|
| Week 1 (1-7 May) | Last squash sowings | Peas, salads, beetroot | Maincrop potatoes (north) |
| Week 2 (8-14 May) | Late cucumbers | Carrots, turnips, swede | Gladioli, perennials |
| Week 3 (15-21 May) | - | Runner beans (south), sweetcorn | Tomatoes (south), summer bedding |
| Week 4 (22-31 May) | - | French beans, runner beans | Courgettes, peppers, dahlias |
How do you protect plants from a late frost in May?
Cover them overnight with horticultural fleece and take it off in the morning. Check the forecast every evening in May, especially on clear, still nights, when frost is most likely. A double layer of fleece gives more protection. Upturned pots, cloches or cardboard boxes work for single plants.
Water in the late afternoon before a cold night, as damp soil holds warmth better than dry. Move pots and baskets against the house wall or into a shed. Gardens in a dip or valley bottom get more frost, so plant out a week or two later there. If leaves do get frosted, leave the plant be. Many bounce back with new shoots once it warms up.
On clear, still May nights, throw fleece over tender plants and take it off in the morning. Upturned pots work well for single plants.
Common mistakes with May planting
Planting out too early
A warm first week of May is very tempting. But ground frost can still hit across much of the UK, and later in the north. One frosty night can kill uncovered tomatoes, courgettes and beans. Check the forecast every night for the first three weeks of May.
Not hardening off properly
Moving plants straight from a warm windowsill to the garden is another classic. The sudden change scorches leaves and stops growth for weeks. Give them 10-14 days to toughen up.
Forgetting to water transplants
New plants need watering every day for the first week, then every 2-3 days for the next fortnight. Their roots are small and can’t reach deeper moisture yet. One missed day in warm weather can finish off a new courgette.
Overcrowding beds
Small plants look lost, so it’s tempting to squeeze them in. They won’t stay small. A courgette fills about 1m, a squash 2m, and runner beans shade everything below them. Follow the spacing on the packet.
Neglecting weeds
May weeds grow as fast as your crops. A quick hoe once a week on a dry day keeps them in check. Leave it a fortnight and you’ll have a carpet of chickweed and fat hen. Little and often beats one huge weeding session.
Next, see what to plant in June, when repeat sowings take over and winter brassica sowing gets going.
Frequently asked questions
When can I plant out tomatoes in May UK?
From late May, once the frosts are over. In southern England that’s usually the second half of May. In the north, wait until late May or early June. Harden them off for 10-14 days first. Tomatoes in an unheated greenhouse can usually go in from early May.
What vegetables can I direct sow in May?
Runner beans, French beans, sweetcorn and courgettes from late May. Keep sowing carrots, beetroot, radish, lettuce, spring onions and spinach too. Turnips and swede go in now for autumn and winter, and quick peas can still be sown.
Is May too late to plant potatoes?
Early May is still fine, even for maincrops. They need about 15-20 weeks to grow, so try to plant by mid-May. Earlies planted now still crop, just later than usual. See our potato timing guide for regional dates.
When should I plant bedding plants outside?
Once the frosts are over, usually the last two weeks of May. Don’t be fooled by a warm spell early in the month, as ground frosts can still strike. If frost is forecast, cover new bedding with fleece overnight.
Can I still sow seeds in May?
Yes, May is a brilliant month for sowing. Warm soil helps seeds come up fast. Runner beans, French beans, sweetcorn and courgettes can all go straight outside from late May. Salads sown now are ready in 4-8 weeks.
What flowers should I plant in May?
Half-hardy annuals like cosmos and zinnias, plus dahlias, after the last frost. Sow sunflowers, nasturtiums and marigolds outdoors. Plant summer bedding and hanging baskets late in the month, and keep planting hardy perennials.
Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
