What to plant in May

May is the busiest month in the vegetable garden. Everything that has been sitting on windowsills and in greenhouses since March can finally go outside. The soil is warm enough for direct sowing of almost anything hardy. And the tender crops - the beans, courgettes, squash, and sweetcorn that frost would have killed in April - are finally safe to plant out.

But May is also the month where people make mistakes. Tender crops go out too early and get caught by a late frost. Seeds rot in soil that looks warm but is not. Seedlings go straight from a heated kitchen to an exposed bed and collapse from the shock. This guide covers what to plant, when, and how to avoid the common traps.

Is it safe to plant outside in May?

For hardy crops, yes - from day one across the whole UK. For tender crops like beans, courgettes, and squash, it depends where you live. Southern England is frost-free by May, but the Midlands and further north may still see frost into mid-May (Met Office regional frost data).

If you are in the south, May is wide open from day one. If you are in the Midlands or further north, treat the first two weeks with caution and keep fleece to hand. In Scotland, the first half of May is still April in practical terms.

How do I harden off seedlings?

Every seedling raised indoors must be gradually acclimatised to outdoor conditions before planting out permanently. A plant that goes straight from a warm windowsill to an open bed will stop growing, wilt, or die. The process takes 10 to 14 days (RHS hardening off guide).

Put plants outside during the day in a sheltered spot. Bring them in at night. Gradually increase their exposure. Only leave them out overnight once night temperatures are reliably above 10 degrees for hardy crops, 12 to 15 degrees for tender ones.

A cold frame makes this easier. A sheltered wall works too. The point is a gradual transition, not a sudden one.

What can I sow directly outdoors in May?

Carrots, beetroot, peas, spinach, perpetual spinach, chard, lettuce, radishes, spring onions, turnips, and parsnips can all go straight into the ground in May. The soil should be at least 7 to 10 degrees Celsius at seed depth (RHS vegetable sowing guide). By early May, UK soil is typically 8 to 12 degrees at 10cm depth, rising to 12 to 16 degrees by late May in southern and central England.

Carrots can be sown throughout May. 1cm deep, thin to 5 to 7cm apart, 15 to 30cm between rows. They take 12 to 16 weeks for maincrops, but baby carrots can be pulled after six weeks. Do not transplant carrots - they fork. Sow direct and thin. Cover with insect mesh to keep carrot root fly off (RHS carrot fly advice). Sow another row in three to four weeks for a succession harvest rather than everything coming at once.

Beetroot goes in 2 to 3cm deep. Each seed is actually a cluster, so you will get multiple seedlings per spot - thin to one or two per station, 10 to 15cm apart. Sow a short row every two to three weeks from May through July and you will be pulling beetroot from midsummer right through autumn. Bolt-resistant varieties like Boltardy are best for early sowings (RHS beetroot guide).

Peas need support from the start - push in sticks or netting at sowing time. 5cm deep, 7 to 8cm apart, in double rows 30cm apart. Early varieties are ready in 12 weeks, maincrops in 14 to 16. Soil needs to be at least 10 degrees. Pick regularly to keep the plant producing. Homegrown peas eaten within an hour of picking are nothing like anything from a supermarket.

Spinach sown in May will bolt faster than spring-sown spinach as the days lengthen and temperatures rise. Sow 2 to 3cm deep, 20cm between rows, and expect three to four weeks of good cutting before it runs to seed. Sow a small amount every two to three weeks. For a spinach-like crop that does not bolt, grow perpetual spinach instead.

Perpetual spinach is technically a chard, not a spinach, but it does the same job without bolting. Sow 2 to 3cm deep, 15 to 20cm apart. It produces pickable leaves for up to ten months from a single sowing and survives mild winters. If you only grow one leafy green, this is the practical choice.

Chard follows the same pattern as perpetual spinach. 2 to 3cm deep, 15 to 20cm apart for salad-sized leaves, 30cm for full plants. Each seed produces multiple seedlings - thin to the strongest. Rainbow chard is attractive enough to grow in a flower border and crops for months.

Lettuce needs barely any covering - scatter seed on the surface and press gently, or cover with the lightest dusting of compost. 15cm apart for loose-leaf types, 30cm for hearting varieties. Sow a pinch every two weeks from May through July. Cut outer leaves and the plant keeps producing. Lettuce bolts in heat, so from June onwards sow in partial shade.

Radishes are ready in four weeks. Sow 1cm deep, thin to 3 to 5cm apart. The fastest crop in the garden and useful as a catch crop between slower-growing vegetables. Sow a short row every two weeks.

Spring onions go in 1cm deep. Sow in clumps of six to eight seeds, 25cm between clumps. Ready in eight to twelve weeks. Keep sowing every three to four weeks through to July.

Turnips are underrated. Sow 1 to 2cm deep, thin to 10 to 15cm apart. Ready in six to ten weeks. Young turnips pulled at golf-ball size are sweet and tender - nothing like the woody things that sit in shops for weeks. You can keep sowing until the end of July.

Parsnips can still be sown in early May. Use fresh seed - parsnip seed loses viability fast (RHS parsnip guide). Sow 1 to 2cm deep, thin to 15cm apart, 30cm between rows. They take three weeks to germinate and need the soil kept moist during that time. You will not be eating them until October at the earliest, and a frost improves their flavour. Late May sowings will give you smaller but still worthwhile roots.

When can tender crops go outdoors?

Runner beans, French beans, sweetcorn, and courgettes need warmer soil and zero frost risk. In southern England, mid-May is usually safe. In the Midlands and north, wait until the last week of May or even early June. Soil temperature needs to be at least 12 degrees for beans and sweetcorn, 15 degrees or above for courgettes (RHS tender vegetable advice). Do not gamble - one late frost kills the lot.

Runner beans are the most productive crop you can grow per square metre. Sow 5cm deep, 15 to 20cm apart, in a double row with a frame of bamboo canes or hazel poles for them to climb. They produce for eight weeks or more if you pick every two to three days - leave pods to mature and the plant stops producing. A row of runner beans in full production generates more food than most people can eat.

French beans go in the same way - 5cm deep, 15cm apart for dwarf varieties, one seed per cane for climbers. Dwarf types do well in containers and raised beds. Climbing varieties produce more over a longer period.

Sweetcorn must be planted in blocks, not rows - it is wind-pollinated and needs neighbouring plants for the cobs to fill (RHS sweetcorn guide). Sow 2 to 3cm deep, 35 to 45cm apart in a grid. Mid-May is the last realistic sowing date for a harvest before autumn. Each plant gives you one or two cobs. Fresh sweetcorn cooked within an hour of picking tastes completely different from anything you have bought.

Courgettes can be direct sown outdoors from late May in the south. Sow 2 to 3cm deep, 90cm apart - they need room. One plant produces 20 to 30 courgettes if you pick them young. Pick at finger-length rather than letting them swell into marrows. Slug protection is essential for the first few weeks - a ring of copper tape or an evening patrol with a torch.

What should I plant out from earlier sowings?

Tomatoes, courgettes, squash, cucumbers, peppers, and chillies that were started indoors in March or April can go out from late May once temperatures are reliably warm. Harden off everything for at least 10 days first.

Tomatoes sown in March or early April can go out from late May once temperatures are reliably above 15 to 16 degrees. Greenhouse planting is safer and earlier than outdoor. Space at 45 to 60cm. Cordon (indeterminate) types need support and side-shooting throughout the season. Bush (determinate) types look after themselves. If you did not sow your own, buy plants now - it is too late to start tomatoes from seed in May and get a worthwhile crop.

Courgettes and squash raised in pots in April go out after your last frost date. Harden off for at least a week first. Courgettes at 90cm spacing, squash and pumpkins at 90cm to 120cm depending on variety. Trailing squash varieties need even more room - or train them up a sturdy frame.

Cucumbers go into the greenhouse from late May or outdoors from early June. 30cm spacing under glass, 60cm outside. They need warmth - night temperatures below 12 degrees will stall them. All-female hybrid varieties produce better and avoid bitter fruit.

Peppers and chillies are greenhouse crops in most of the UK. Plant out into the greenhouse from late May at 38 to 45cm spacing. Outdoor growing works in the south in a sheltered, sunny spot, but yields are lower and ripening is slower. If you have not already sown these, buy plants - May is far too late to start from seed.

What winter crops should I start now?

May is not just about summer eating. Brussels sprouts, kale, leeks, savoy cabbage, calabrese, and swede started now will keep you fed from November through March. Getting these in during May gives them the long growing season they need to bulk up before winter (RHS winter vegetable guide).

Brussels sprouts sown in modules now will be transplanted in June or July and ready from November. They need serious space - 60 to 75cm each way. A single stalk produces 50 to 60 sprouts and frost improves their flavour. Start them now or miss the window.

Kale started in May modules and planted out in June will crop from autumn right through winter and into the following spring. 45 to 60cm spacing. Virtually indestructible once established. Protect with insect mesh against cabbage white butterflies.

Savoy cabbage and winter cabbage sown in modules in May, transplanted in June, give you dense heads through the coldest months. 45 to 50cm spacing. Get them sown by early June at the latest - they need time to form proper hearts before autumn.

Calabrese broccoli is faster than sprouting broccoli - ready in about 14 weeks from sowing. Module-sow in May, transplant in June at 25 to 55cm spacing depending on how large you want the heads. Cut the central head first and side shoots follow.

Leeks sown in modules now (four seeds per cell, do not thin) will be transplanted into deep holes in June or July. Drop the seedling in, water it, and let the hole fill naturally over time to blanch the stem. They stand through the worst winter weather and are available fresh when almost nothing else is.

Swede is sown at the end of May or early June. One seed per module, planted out at 30cm spacing. Not ready until autumn, and like parsnips, the flavour improves after a frost.

What is too late to start in May?

Not everything is still possible. These crops needed an earlier start and attempting them now will waste time and growing space.

• Garlic - should have gone in during autumn or very early spring. May is too late.

• Onions from seed - needed to be sown in January to March. Onion sets can still go in during early May.

• Peppers and chillies from seed - need 18 to 24 weeks to harvest (RHS chilli guide). Buy plants instead.

• Aubergines from seed - same issue. Greenhouse plants only in most of the UK anyway.

• Tomatoes from seed - marginal. Buy young plants from a garden centre if you have not already started them.

• Broad beans - can still be sown in very early May, but they perform best from autumn or early spring sowings. After mid-May, do not bother.

• Early potatoes - should have been planted in March or April. Maincrop potatoes can still go in during the first week of May.

How does succession sowing work?

The biggest mistake in May is sowing everything at once. You end up with a mountain of lettuce in July and nothing in September. Instead, sow small amounts of fast-growing crops every two to four weeks to spread the harvest across the whole season (RHS succession sowing guide).

A useful trigger: sow the next batch when the previous sowing has four true leaves (for leafy crops), or when peas reach 5cm and beans reach 10cm. That spaces things out naturally based on actual growing speed rather than a rigid calendar.

May sowing reference table

Depths and spacings based on RHS vegetable sowing recommendations.

Where should I start if this is my first year?

If this is your first May in the garden, do not try to do everything. Pick a handful of crops and do those properly.

The highest-return choices for a new grower starting in May:

• Runner beans - the most food for the least effort once they get going

• Courgettes - one plant, dozens of harvests

• Beetroot - reliable, forgiving, and ready in under ten weeks

• Lettuce - sow a pinch every fortnight and you will not buy salad all summer

If you started things in April, May is about getting them outside safely and filling any gaps with direct sowings. If you are starting from scratch, May is actually the ideal month - the soil is warm, the frost risk is fading, and there is still time for everything except the longest-season crops.

Logging what you sow and when it actually produces is how you turn a first season into a system. myPatch tracks your beds, your sowings, and your local weather - so next year you already know what worked and when to start it.

May is the month the garden stops being a plan and starts being a patch.