One thing to be careful of in early May is frost. It can still happen, especially in the north and on higher ground. Tender plants put outside too soon can get damaged overnight even when the days feel warm. From late May the risk mostly disappears and you can plant out far more freely.

This guide covers what flowers to plant in May in the UK, kept as simple as possible. For everything else going on in the garden in May, What to Plant in May in the UK has the full picture.

Easy Flowers to Sow Directly Outside in May

These are seeds you can put straight into the ground outside in May. No pots, no indoor starting, no fuss. They grow quickly in warm soil and most will be flowering in about 8 weeks.

Nasturtiums are the easiest flower you can grow. Push the seeds into the soil where you want them, water them in, and that is pretty much it. They come up within a week and flower all summer. They are also really useful near vegetables because they attract aphids away from other plants. You can eat the flowers and leaves too.

Cornflowers are also very easy. Sow them thinly, thin them out a bit once they come up, and deadhead them regularly to keep the flowers coming. They produce blue, pink, and white flowers from July right through to the first frosts.

Calendula (pot marigold) is bright, cheerful, and hard to get wrong. Sow directly outside, give them a bit of space, and keep deadheading. The petals are edible and work well in salads.

Sunflowers can go straight outside in May once the risk of frost has passed. They do not do well if transplanted so put them where you want them to grow. Give them a sunny spot and some shelter from wind if you can, as tall varieties can fall over before they get established.

Annual poppies just need scattering onto prepared soil and a light rake over the surface. They do not like being moved so sow them where they are going to flower. They come up quickly and give a good show through summer.

Borage is a brilliant flower to grow near a vegetable patch. Bees love it, it is very easy from seed, and once it is happy it tends to come back on its own each year.

Phacelia is less well known but bees love it even more than borage. It grows fast from seed sown directly in May and is one of the best flowers for attracting useful insects to the garden.

For the full vegetable sowing guide to go alongside your flowers, What to Sow in May in the UK covers every crop worth getting in the ground this month.

Bedding Plants to Plant Out in May

Bedding plants are flowers that were started indoors earlier in the year and are now ready to go outside. The main thing to know is that these plants cannot cope with frost. Do not put them outside for good until late May, when overnight temperatures are reliably above 10 degrees.

Before you plant them out permanently, it helps to harden them off. This just means putting them outside during the day and bringing them back in at night for a week or two. It sounds like extra work but it really does help them settle in much faster once they are out for good.

If you are not sure when your last frost is likely to be, UK Last Frost Dates by Postcode is useful.

Marigolds are one of the most popular flowers for May planting. French marigolds are compact, flower for months, and are great to grow near tomatoes. Plant them out from late May.

Cosmos are tall and airy with flowers in pink, white, and deep red. They are great for cutting and flower right through summer and autumn. Plant out from late May and keep deadheading.

Antirrhinums (snapdragons) are reliable and colourful. They like a sunny spot and well-drained soil. Plant out from late May.

Petunias are one of the best flowers for pots and hanging baskets. They produce masses of flowers all summer. Plant out from late May. They need regular watering and a weekly liquid feed from June to keep performing well. How Often to Water Plants in the UK has more on keeping container plants happy.

Busy lizzies are ideal for shady spots where most flowers struggle. They flower all summer and do well in pots. Plant out from late May and keep them well watered.

Summer Bulbs to Plant in May

May is the main time to plant summer-flowering bulbs. These are different from spring bulbs like tulips which go in during autumn. Summer bulbs get planted in May and flower later in the year.

Dahlias are worth every bit of effort. They flower from July right through to the first frosts and the range of colours and shapes is huge. Plant the tubers about 10cm deep in a sunny sheltered spot from late May once the frost risk has gone. Do not rush them out early as they are not frost hardy.

Gladioli are good for cutting and easy to grow. Plant the corms about 10cm deep in a sunny spot. Planting a small batch every couple of weeks through May and June gives you flowers over a longer period rather than all at once.

Begonias (tuberous types) can go outside in late May in sheltered spots or containers. They are one of the better options for partial shade and flower well into autumn.

Flowers for Pots and Containers in May

Most of the bedding plants above work well in pots and containers. Petunias, marigolds, cosmos, and busy lizzies all do well in pots on a sunny patio or doorstep.

The main difference with container growing is watering. Pots dry out much faster than the ground, especially in warm weather. In summer you will probably need to water every day. A weekly liquid feed from June also makes a big difference to how many flowers you get. Without feeding, plants in pots run out of nutrients quite quickly and the flowering drops off.

Flowers to Grow Near Vegetables

If you grow vegetables as well, it is worth planting a few flowers nearby. It is not complicated. A few simple choices make a real difference.

Nasturtiums are the most useful. They attract aphids away from beans and tomatoes and bring in insects that eat aphids. They are also good for pollinators.

Marigolds are popular near tomatoes. Whether they actually deter whitefly is debated but they do attract useful insects and look good.

Borage and phacelia both bring large numbers of bees into the garden which helps all your flowering crops, and they are two of the easiest bee friendly plants to start with.If slugs are causing problems, How to Get Rid of Slugs in the Garden covers the best methods. Young flower seedlings are just as vulnerable as vegetable seedlings in the first few weeks.

Do Not Rush Tender Plants Outside Too Early

The most common mistake in May is putting tender plants outside before the cold weather has properly gone. A sunny warm day can make it feel like summer but one cold night can set plants back badly or damage them completely.

Check overnight temperatures, not just daytime ones. Below 5 degrees is risky for most tender plants. If frost is forecast after you have already planted out, How to Protect Vegetables from Frost in the UK covers what you can do quickly. The same methods work for flowers.

FAQs

A Sensible Place to Start

May is one of the best months for flowers. Hardy annuals like nasturtiums, cornflowers, and calendula can go straight in the ground right now. Bedding plants like marigolds and cosmos follow in late May once the frost risk has gone. Summer bulbs like dahlias go in now too and will be flowering by mid-summer.

If you are not sure where to start, a few nasturtium seeds pushed into the soil near your vegetables is genuinely one of the best things you can do in May. They come up fast, look good, help the garden, and ask for almost nothing back.

For more on what is worth doing in the garden this month, May Gardening Jobs in the UK and What to Sow in May in the UK cover the full picture.

The other thing that makes May useful is variety. You can sow fast crops like salad leaves and radishes that will be ready in weeks. You can sow slower crops like carrots and beetroot that will fill the veg patch through summer and autumn. You can start leeks and brassicas that won’t be harvested until winter. And you can get flowers in the ground that will be blooming by July. All in the same month, in the same beds, without a greenhouse in sight.

This guide covers what to sow in May in the UK in detail, crop by crop, so you know exactly what goes in the ground now, what to start indoors, and what to avoid rushing before conditions are ready. For a broader look at everything you can do in the garden this month beyond just sowing, May Gardening Jobs in the UK covers the full picture.

Getting the Soil Ready Before You Sow

Before anything goes in the ground it’s worth spending ten minutes on the soil. You don’t need to dig everything over or add bags of compost before every sowing, but a bit of basic preparation makes a real difference to how well seeds germinate.

The main thing you want for direct sowing is a fine, crumbly surface that seeds can make good contact with. If your soil is lumpy, compacted, or has a crust from recent rain, break it up with a rake and work it into a reasonable tilth before sowing. Seeds that sit in air pockets or can’t contact moist soil consistently will germinate patchily or not at all.

If a bed has had nothing added to it for a while, working in some compost before sowing is worthwhile. It doesn’t need to be a deep dig, just mixing some into the top layer where the seeds will sit. How to Improve Garden Soil in the UK covers the practical side of this, and Best Compost for Vegetables in the UK covers what’s actually worth buying.

One more thing: check moisture levels before sowing. The soil should be damp but not wet. If it’s dry, water it a day before sowing rather than after, so the moisture is evenly distributed through the surface layer when the seeds go in.

Vegetables to Sow Directly Outside in May

Direct sowing means putting seeds straight into the ground outdoors rather than starting them in pots or trays. May is the best month of the year for this because soil temperatures are high enough for seeds to germinate quickly without rotting, and the weather is generally warm enough to keep growth moving.

Carrots

Carrots are one of the most rewarding things to sow in May. Germination is far more reliable now than in March or April when the soil is still cold and wet, and you get much less of the patchy, uneven emergence that frustrates early season sowing.

Sow thinly into drills about 1cm deep and 30cm apart. Carrots don’t like transplanting so they need to go straight into their final position. Thin to about 5-8cm apart once they’re established, or you’ll get lots of small, twisted roots fighting for space.

One of the best things you can do with carrots is sow in succession, a short row every two to three weeks through May and into June, rather than sowing a large amount all at once. You end up with harvests spread over months rather than everything coming ready at the same time. When to Plant Carrots in the UK covers the timing in full.

Beetroot

Beetroot is probably the most beginner-friendly crop you can sow in May. It germinates quickly in warm soil, grows without drama, tolerates a certain amount of neglect, and produces harvests you can actually use in the kitchen. If you’re not sure where to start in May, beetroot is always a safe choice.

Sow about 2cm deep in rows 30cm apart. Each beetroot “seed” is actually a cluster of seeds, so you’ll almost always get more than one seedling per planting position. Thin down to one plant per position once they’re a few centimetres tall. Like carrots, succession sowing every two to three weeks gives you a much more manageable harvest. When to Plant Beetroot in the UK has the full timing guide.

Peas

Early May is still within the pea sowing window, but it is the tail end of it. Peas prefer cooler growing conditions and once summer heat arrives they struggle, so anything sown after mid-May is a bit of a gamble depending on your location. Get them in during the first two weeks of May for the best results.

Sow about 5cm deep in double rows, with seeds roughly 8cm apart within the row. Peas need support as they grow, so put canes or pea sticks in at sowing time rather than waiting until they’re already flopping over. When to Plant Peas in the UK explains the window clearly and what to expect from later sowings.

French Beans

French beans are a warm-soil crop and mid-May is the earliest you should sow them outdoors. Any earlier and the seeds tend to sit in the ground without germinating, or they rot before they get the chance. The difference between sowing French beans in late April and mid-May is often the difference between success and a failed sowing.

Sow about 5cm deep in rows 45cm apart, with seeds roughly 15cm apart in the row. They grow quickly once conditions are right and you can expect to be harvesting within 10-12 weeks of sowing. Climbing varieties need support; dwarf varieties are more compact and don’t need staking. When to Plant French Beans in the UK covers the timing in detail.

Runner Beans

Runner beans follow the same logic as French beans, mid to late May for outdoor sowing, once the soil is warm and overnight temperatures have settled above 10°C. They’re one of the most productive crops in a UK vegetable garden, and a couple of plants will produce more beans than most families can keep up with through summer.

Sow 5cm deep, about 15-20cm apart along a row of canes or a wigwam structure. Put the supports in before or at the same time as sowing, not after, so you’re not disturbing roots later. Water well after sowing and keep an eye on soil moisture in the first few weeks. When to Plant Runner Beans in the UK has the full timing guide.

Salad Leaves and Lettuce

Salad leaves, cut-and-come-again mixes, spinach, and lettuce are among the fastest and most satisfying crops to sow in May. Germination is quick, harvests can start within four to six weeks of sowing, and you can cut the leaves repeatedly rather than pulling the whole plant.

Scatter seeds thinly over a prepared bed or sow in shallow drills about 1cm deep. Thin once seedlings are a few centimetres tall. Like carrots and beetroot, succession sowing a small amount every couple of weeks makes much more sense than sowing a large amount at once and ending up with more salad than you can eat before it bolts.

Spinach is worth growing separately from salad mixes as it has slightly different needs, it prefers not to dry out and can bolt quickly in hot, dry conditions. When to Plant Spinach in the UK covers the timing and how to manage it through summer. For lettuce specifically, When to Plant Lettuce in the UK explains the best varieties for May sowings.

Spring Onions and Radishes

Both of these are worth sowing if you want something genuinely quick. Radishes can be ready in as little as four weeks from sowing in May, making them one of the fastest crops in the kitchen garden. Spring onions take a little longer, around eight weeks, but they’re dependable and can be used fresh from the ground.

Sow radishes thinly in shallow drills and thin to about 3cm apart once germinated. Don’t leave them in the ground too long once they’re ready, they turn woody and unpleasant within days of reaching harvest size. Sow a small amount every ten days for a continuous supply rather than a single large sowing.

Courgettes

Courgettes can be sown directly outside from late May in sheltered, mild gardens. Most people start them indoors in April for planting out in May, but if you haven’t done that, a direct outdoor sowing in the last week of May is perfectly viable in most UK gardens. They germinate fast once soil temperatures are consistently above 15°C.

Sow two seeds per position, about 2cm deep, and remove the weaker of the two seedlings once they’re established. Give each plant plenty of room, they spread considerably. How to Grow Courgettes in the UK covers the full process from sowing to harvest.

Sweetcorn

Late May is the right time to sow sweetcorn directly outside in warmer parts of the UK. In the north or on exposed sites it’s safer to start indoors in late April or early May and plant out in June. Sweetcorn is wind-pollinated and needs to be grown in a block, not a single row, so each plant pollinates its neighbours.

Sow 2.5cm deep in a grid pattern with about 45cm between plants. They need a warm, sheltered spot and consistent moisture to crop well. Don’t bother growing sweetcorn in a cold or shaded garden, it just doesn’t produce enough in poor conditions to be worthwhile. How to Grow Sweetcorn in the UK covers the full process from seed to harvest.

Potatoes

Maincrop potatoes can still go in during early May in most UK gardens, particularly in northern areas where later planting is normal. If you’re in the south and haven’t planted yet, early May is getting late for maincrops but still worth doing. First and second earlies planted now will produce a later harvest than usual but will still crop. When to Plant Potatoes in the UK covers the full timeline by variety and region.

Flower Seeds to Sow in May in the UK

May is an excellent month for sowing flowers directly outside. Hardy annuals in particular do well when sown now, they establish quickly in warm soil and most will be flowering by July or August. For the full guide including bedding plants and summer bulbs, What Flowers to Plant in May in the UK goes much deeper into flowers specifically.

Nasturtiums

Nasturtiums are almost impossible to fail with in May. Sow them where you want them to flower, cover lightly with soil, and water in. They germinate within a week in warm conditions and produce flowers from June onwards. They work well in vegetable gardens too, attracting aphids away from other crops and bringing in beneficial insects.

Cornflowers

Cornflowers sown directly in May will flower from July and keep going until the first frosts. Sow thinly in drills, thin to about 15cm apart, and deadhead regularly to keep them producing. They’re fully hardy and ask for very little once established.

Calendula

Calendula (pot marigold) is another May sowing that gives a lot back for very little effort. Sow directly outside, thin to 30cm apart, and deadhead regularly. Like nasturtiums, they work well alongside vegetables and are edible, the petals can be used in salads.

Sunflowers

Sunflowers can be sown directly outside in May once frost risk has passed. Sow 2.5cm deep in their final position as they don’t transplant well. Give them full sun and shelter from wind if possible. They’re one of the most satisfying plants to grow from seed and children in particular love watching them develop.

Borage, Phacelia, and Annual Poppies

All three of these can be scattered directly where you want them to flower in May. They germinate readily in warm soil and are excellent for attracting pollinators. Borage in particular is worth growing near vegetable beds as it draws bumblebees and other beneficial insects.

What to Sow Indoors or Under Cover in May

Not everything sown in May goes outside immediately. A few crops benefit from being started indoors or under cover in May for planting out later in the season.

Leeks

Leeks are a long-season crop that need starting in May to give them enough time to develop before autumn. Sow thinly in a seed tray or small pot indoors and they’ll be ready to plant out into their final positions in June or July. They’re one of the most dependable winter vegetables and well worth the growing time. When to Plant Leeks in the UK covers the full sowing and planting schedule.

Kale and Purple Sprouting Broccoli

Kale and purple sprouting broccoli both need to be started in May if you want harvests through winter and early spring. Sow in individual pots or a seed tray under cover and plant out in June once they’ve developed a few true leaves. These are tough, reliable crops that occupy space in the garden for a long time, so it’s worth getting the timing and spacing right before committing. When to Plant Brassicas in the UK covers the full schedule for all brassica types.

Brussels Sprouts

If you want Brussels sprouts for Christmas, May is genuinely your last chance to sow them. They need a very long growing season, around six months from sowing to harvest, so seeds going in now will produce sprouts from November onwards. Start indoors or under cover and plant out into a firm seedbed in June.

Basil

Basil needs warmth to germinate well and is best sown indoors in May rather than outside. Full timing guidance is in When to Plant Basil in the UK, and How to Grow Basil from Seed in the UK covers the full process from sowing through to harvest. It’s one of the most temperature-sensitive herbs and even a mild cold snap outdoors can check its growth badly. For the wider picture across all UK herbs, see growing herbs at home. Sow in small pots on a warm windowsill, keep it there until June, and only move it outside once you’re sure overnight temperatures have settled.

Succession Sowing in May

One of the most useful habits to get into with May sowing is thinking in terms of succession rather than single large sowings. The idea is simple: instead of sowing a whole row of carrots or a large patch of salad in one go, you sow a small amount and then sow another small amount two to three weeks later, and so on through the growing season.

The result is that you get a steady supply of crops coming ready at different times rather than everything being ready at once. This is particularly useful for fast-growing crops like radishes, salad leaves, spring onions, and lettuce, where a single large sowing can produce more than you can use before it goes past its best.

For slower crops like carrots and beetroot, succession sowing spreads the harvest across a longer period and also means that if one sowing is hit by pests or bad weather, you haven’t lost everything.

Common Sowing Mistakes in May

A few mistakes come up repeatedly in May that are worth knowing about before you start.

Sowing too deep. Most vegetable seeds are smaller than you think and don’t need to go in very deep. The general rule is to sow at a depth of roughly twice the diameter of the seed. Sowing too deep means seeds have to push through too much soil before they reach light, and many don’t make it. If in doubt, sow shallower rather than deeper.

Sowing too thickly. It’s tempting to sow generously to make sure you get enough plants, but overcrowded seedlings are harder to thin, compete badly with each other from the start, and are more vulnerable to fungal problems caused by poor air circulation. Sow thinly and thin properly once they’re established.

Not watering after sowing. Seeds need consistent moisture to germinate. A dry spell right after sowing can stop germination altogether, or worse, start it and then kill the seedlings before they reach the surface. Water the bed gently after sowing and keep the soil evenly moist until germination is underway. How Often to Water Plants in the UK covers the detail on watering through the growing season.

Forgetting to thin. Thinning is the job most beginners skip or put off, and it shows in the final harvest. Crowded seedlings produce small, misshapen crops and are more prone to disease. Thin properly to the recommended spacing and resist the urge to leave them all in hoping they’ll find their own space. They won’t. When to Thin Vegetable Seedlings in the UK explains how to do it without second-guessing yourself.

Sowing warm-season crops too early in May. French beans, runner beans, and courgettes all need warm soil to germinate properly. Sowing them in early May when soil hasn’t fully warmed often results in failed germination or rotting seeds. Wait until mid to late May for these crops and the success rate improves significantly.

Protecting May Sowings from Pests

Two pests are worth thinking about whenever you sow in May.

Slugs are at their worst in warm, damp conditions and young seedlings emerging in May are exactly what they’re looking for. A row of carrot seedlings can disappear overnight if slugs are active in your garden. Check after dark to get a sense of numbers and deal with them before they establish. How to Get Rid of Slugs in the Garden covers the methods that actually make a difference.

Birds can also be a problem with freshly sown beds, particularly for peas and beans where they’ll pull seeds straight out of the ground. A simple covering of netting or a few twiggy sticks pushed into the soil around the sowing area is usually enough to deter them while seeds germinate and establish.

FAQs

A Sensible Place to Start

May gives you more sowing options than any other month in the UK gardening year. Hardy crops like carrots, beetroot, and salad leaves can go straight in the ground right now. Slightly more demanding crops like French beans and runner beans can follow from mid to late May once the soil has properly warmed. Flowers like nasturtiums and cornflowers can go in whenever you’re ready. And slower crops like leeks and brassicas are worth getting started indoors this month for harvests later in the year.

The thing to avoid is trying to do everything at once in the first week of May. Stagger your sowings, do a little at a time, and build in succession sowings for the faster crops. It takes about the same amount of effort as doing it all in one go, and the results over the next four to five months are considerably better.

If you’re not sure where to begin, start with three crops: beetroot, salad leaves, and nasturtiums. All three are low risk, quick to germinate, and immediately rewarding. Once those are in the ground and growing the rest of the season tends to take shape naturally. For everything else worth doing in the garden beyond sowing this month, May Gardening Jobs in the UK covers the full picture. And for the full year of sowing and harvest dates on one page, bookmark the our month-by-month sowing guide.