What to Plant in March

Vegetables to Sow and Plant in March

March is when the UK growing season truly gets going. The soil is warming, daylight hours are increasing, and there is a huge range of vegetables you can start this month. Whether you have a greenhouse, a sunny windowsill, or just an open plot, there is plenty to get on with.

Hardy Vegetables to Sow Outdoors

These crops can handle the cold March soil and even a light frost, so they go straight outside. The key is soil temperature — most of these need the ground to be at least 5-7°C. If your soil is still frozen or waterlogged, wait a week or two rather than forcing seeds into cold, wet ground.

Broad beans are one of the most rewarding March sowings. Push seeds 5cm deep and 20cm apart in double rows. They are completely hardy and will shrug off any late frost. Choose varieties like Aquadulce Claudia or The Sutton (a dwarf variety ideal for small plots and windy sites).

Peas can go in from mid-March. Sow 5cm deep in a flat-bottomed trench, spacing seeds 5-7cm apart. Put supports in at sowing time — it is much easier than trying to retrofit them once the plants are climbing. A 1.5m row yields roughly 2-3kg of peas.

Parsnips need to go in now. They are notoriously slow to germinate (2-4 weeks), so sow 3-4 seeds per station, 1.5cm deep, and thin to the strongest seedling. Always use fresh seed — parsnip seed loses viability after one year.

Carrots can be sown from mid-March under cloches or fleece. Sow thinly in rows 15cm apart, just 1cm deep. The biggest mistake is sowing too thickly — you will spend hours thinning, and thinning disturbs the soil, which attracts carrot fly.

Radishes, lettuce, rocket, spinach and spring onions are all quick crops that can go outdoors now. Radishes are ready in just 4 weeks — sow a short row every fortnight for a continuous supply. Lettuce and rocket can be sown in shallow drills and will give you salad leaves within 4-6 weeks.

Onion sets and turnips also go in this month. Push onion sets into prepared soil so the tip is just visible. Turnips are sown 1cm deep in rows 25cm apart — they are underrated and grow fast.

Indoor Sowing: Windowsill and Greenhouse

March is the month to start your tender crops indoors. A warm windowsill (15-21°C) or a heated propagator is all you need. These plants will not go outside until after the last frost in May, so you are giving them a 10-12 week head start.

Tomatoes are the big one. Sow seeds 1cm deep in small pots or module trays filled with seed compost. Keep at 18-21°C and they will germinate in 7-10 days. Once seedlings have two true leaves, pot on into 9cm pots. Do not sow too early — leggy, overgrown seedlings by May are worse than compact, stocky ones.

Peppers and chillies need warmth to germinate — at least 18°C, ideally 21-25°C. They are slower than tomatoes (10-14 days to germinate) and grow more slowly, so getting them started now is important. A heated propagator makes a real difference.

Cucumber seeds are large and easy to handle. Sow one seed per 9cm pot, pointed end down, 2cm deep. They germinate quickly at 20°C. Do not start cucumbers too early — they grow fast and will outgrow your windowsill before May if you are not careful.

Broccoli, cauliflower, Brussels sprouts, cabbage and leeks can all be started in module trays this month. These brassicas and alliums are slower-growing and benefit from a long season. Sow into modules filled with multipurpose compost — you will pot them on or plant them out as they develop.

Need to work out how much compost to buy? Use our compost calculator to get the exact volume for your seed trays, pots or raised beds.

Planting Out

First early potatoes can go in from late March in southern England. Plant seed potatoes 12-15cm deep and 30cm apart in rows 60cm apart. Ideally, you have been chitting them since late January — the sprouts should be 2-3cm long and sturdy. Varieties like Swift, Rocket and Casablanca are good first earlies that will be ready to harvest from June.

Onion sets and shallots can be planted out now if you have not already done so. Space onion sets 10cm apart in rows 30cm apart. Shallots need a bit more room — 15cm apart. Push them gently into the soil so the tip is just visible.

If you are preparing new beds, our soil calculator will tell you exactly how much topsoil or compost you need to fill them.

Quick Wins: Fastest Crops to Start in March

If you want fast results, these are the crops to prioritise this month:

• Radishes — ready in just 4 weeks from sowing. Sow outdoors, 1cm deep, and thin to 3cm apart.
• Rocket — cut-and-come-again leaves ready in 3-4 weeks. Sow in a shallow drill or scatter in a pot.
• Lettuce — baby leaves in 4-5 weeks. Sow in succession every 2-3 weeks for a constant supply.
• Spring onions — ready in 8-10 weeks. Sow in clumps of 6-8 seeds, no need to thin.
• Spinach — quick-growing baby leaves in 4-6 weeks. Prefers cooler weather, so March is ideal.

These are perfect for impatient gardeners, children, or anyone new to growing their own.

Flowers to Sow in March

March is not just about vegetables. Getting flowers started now means colour from June onwards, and many will attract pollinators that help your vegetable crops too.

Hardy Annuals to Sow Outdoors

These tough plants can handle March temperatures and will flower from June through to autumn. Prepare the ground by raking to a fine tilth and scatter seeds thinly, or sow in drills and thin to the spacing on the packet.

Cornflowers are one of the easiest annuals to grow and come in blues, pinks and whites. Calendula (pot marigold) is almost impossible to kill and self-seeds freely. Poppies — both Californian and field poppies — need a sunny, well-drained spot. Nigella (love-in-a-mist) gives you delicate blue flowers followed by attractive seed pods. Sweet peas sown now will flower from June — soak the seeds overnight before sowing for better germination.

Half-Hardy Annuals to Start Indoors

These need the protection of a windowsill or greenhouse until after the last frost. Sow into modules or small pots of seed compost and keep at 15-20°C.

Cosmos is the cottage garden staple — easy, elegant, and flowers until the first frost. Zinnias are spectacular cut flowers that love hot summers. Dahlias can be started from seed in March for flowers by late summer. Marigolds (French and African) are brilliant for containers and for companion planting alongside tomatoes to deter whitefly.

Bulbs to Plant

March is the time to plant summer-flowering bulbs. Gladioli corms go 10-15cm deep and 10cm apart — plant in batches every two weeks for a succession of flowers. Lilies can be planted in pots or in the ground, 15cm deep in well-drained soil. Ranunculus tubers can go in now in a sheltered spot for cut flowers later in summer.

Fruit and Soft Fruit in March

March is your last chance to plant bare-root fruit trees and bushes before they break dormancy. Once buds start to open, bare-root planting becomes unreliable — switch to container-grown plants instead.

Raspberry canes can still be planted. Space them 40-50cm apart in rows, with 1.5-1.8m between rows. Cut autumn-fruiting varieties down to ground level after planting. Summer-fruiting varieties should be cut to 25cm above ground.

Strawberry runners planted now will give you a small crop this summer and a full crop next year. Plant with the crown at soil level — too deep and they will rot, too shallow and they will dry out.

Gooseberry and currant bushes (blackcurrants, redcurrants, whitecurrants) can go in now. Mulch around the base with a 5-8cm layer of bark mulch or well-rotted compost to retain moisture and suppress weeds. Use our mulch calculator to work out how much you need.

Rhubarb crowns can be planted or divided this month. Plant with the growing point just above soil level and space them 90cm apart — they need room to spread.

Regional Planting Adjustments

The timings above are based on average conditions in central and southern England. The UK is a large country with significant climate variation, so adjust your sowing dates based on where you garden.

The most reliable indicator is your local soil temperature. You can buy a soil thermometer for a few pounds — it takes the guesswork out of sowing. Most vegetable seeds need at least 5°C for germination, and many perform much better at 10°C or above. If your soil is not warm enough, use cloches or horticultural fleece to raise the temperature by 2-3°C.

Common March Planting Mistakes

March is exciting — it feels like the growing season is finally here — but rushing can cost you. These are the five most common mistakes UK gardeners make this month.

1. Sowing tender crops outdoors too early. Tomatoes, courgettes, peppers and beans cannot survive frost. They should only be sown indoors in March, and planted outside after the last frost in mid to late May. Every year, gardeners lose seedlings to an unexpected April frost because they jumped the gun.
2. Not hardening off seedlings. Plants raised indoors need a gradual transition to outdoor conditions. Put them outside during the day and bring them in at night for at least 7-10 days before planting out permanently. Skip this step and you will shock the plants, stunting their growth.
3. Sowing too deep or too shallow. The general rule is to sow seeds at a depth of twice their diameter. Tiny lettuce and carrot seeds go on the surface with a light dusting of compost. Peas and broad beans go 5cm deep. Burying fine seeds too deep means they will never see daylight.
4. Overwatering seedlings indoors. More seedlings are killed by overwatering than underwatering. Keep compost moist but not waterlogged. Good drainage is essential — use module trays with drainage holes and never let pots sit in saucers of water for extended periods.
5. Forgetting frost protection. March nights can still drop below freezing. Cover outdoor sowings with fleece or cloches. Keep fleece handy for sudden cold snaps right through to mid-May. A single hard frost can wipe out a row of seedlings that took weeks to establish.

Frequently Asked Questions

Where to Buy Seeds in the UK

Ready to start sowing? These UK suppliers stock seeds, starter kits and everything you need for March planting.

Links marked above are affiliate links — we may earn a small commission at no extra cost to you. We only link to reputable UK suppliers.

Useful Gardening Tools

Planning your March planting? These free calculators will help you work out exactly how much you need.