What to Sow in February – The Complete UK Guide to February Sowing

The difference between January and February is daylight. You can see it happen: the seedlings on the windowsill start reaching at a shallower angle, the colour coming in a little stronger. That pale, drawn look in seedlings that have been sitting in the dark for three weeks starts to ease off. February is when the season properly opens, not as an act of optimism but because the light has genuinely improved enough to support it.

It’s the month that most crops can realistically start. Chillies and habaneros and exhibition onions had to go in January because of the time they need. Everything else (tomatoes, leeks, onions from seed, celeriac, cauliflower, antirrhinums, sweet peas) starts in February either because it genuinely needs those weeks or because February gives it the best head start. This guide covers each of them, what they specifically need, and why.

Tomatoes: late February for the greenhouse, March for everyone else

Greenhouse growers should start tomatoes in late February. Not early February, not the 1st of February. Late February. The window exists because a greenhouse-grown plant can go into its final position from late April, which means a late-February sowing gives exactly the 8-10 weeks of indoor growing those plants need. If you sow earlier, the plants outgrow their pots before there’s anywhere to put them, and a root-bound tomato that spends three weeks recovering is not ahead of anything.

For outdoor growing, wait until early-to-mid March. The outdoor planting date (late May in the south, early June in the north) is what determines the sowing date, not enthusiasm. Count back 8-10 weeks from when you can realistically plant out. That sum doesn’t come out to early February for any outdoor UK grower.

A heated propagator at a consistent 20°C gives you 90% germination or better in 7-14 days. A windowsill gives you 60%, because the temperature drops overnight and stalls the seeds each time. That’s not a minor difference. When the seedlings are up, get them off the propagator immediately. High warmth plus February’s still-improving light is the recipe for the long, thin, pale seedlings that struggle when they finally get outside. Drop the temperature to 15-18°C during the day and 12-15°C at night. Cooler nights produce stockier, stronger stems. Every source says this and most people ignore it because cooler feels wrong when you want the plants to grow. The plants grow better for it.

Pot on to a 7cm pot at the first true leaves. Pot on again to 12cm when roots fill that. Never skip a stage to save time. A tomato that’s forced into a large pot before it can fill a small one sits in cold compost it can’t reach and sulks for a week. Gradual stages build the root system that actually supports a heavy-cropping plant.

Leeks: module sowing, the dibber method, and why you don’t backfill

February is the right time to start leeks from seed, and a row of twenty plants sown now and transplanted in June gives you fresh leeks from October through to the following April. That’s six months of harvests from one sowing session.

Sow in module trays at 12-15°C. No heat needed. Two or three seeds per cell at 1cm depth. Germination takes 14-21 days. Keep them cool and bright. Leeks started in warmth get leggy in the same way brassicas do, and a leggy leek seedling makes a poor transplant. When they’re pencil-thick (around 6-8mm) and about 15-20cm tall, they’re ready to go out.

The dibber method is the one to use. Make holes 15cm deep with a dibber, trowel handle, or the blunt end of a cane. Drop one seedling into each hole so the roots touch the bottom. Now water each hole, filling it almost to the top. Then leave it. Do not push soil back in. This is the part that trips people up. The hole fills naturally over weeks as the plant grows and the rain works soil inward. The developing stem is in the dark for that whole time, which is how you get the long white blanched shank. Backfilling the hole at planting time traps grit between the leaf layers, and you spend the winter trying to wash it out in the kitchen.

Space plants 15cm apart in rows 30cm apart. Earth up in July and August by drawing soil around the stems as they thicken. Each session adds more to the white shank.

Two pests worth knowing about. Leek rust shows as orange pustules on the leaves from late summer. It rarely kills the plant or affects eating quality, but it does look alarming, and it’s worse in warm humid conditions. For late varieties, Bandit has good resistance. Allium leaf miner is active twice a year: March to April and October to November. The larvae tunnel into the stems and cause brown-streaked damage that opens the door to rot. There’s no chemical control available to home growers. Fine insect mesh over the crop during those two periods is the only effective prevention.

Onions and celeriac: two crops that need different things from February

Onions from seed want to go in during the first week of February. Not mid-February, not late February. The first week. They like cooler conditions than you might expect: 10-15°C, not the warm propagator temperatures that chillies and peppers need. Sow two seeds per 8cm pot in seed compost, cover with 1.5cm of compost, and water from below by standing the pots in a container of water rather than pouring from above. Thin to the strongest seedling as soon as you can.

The reason to thin promptly, and to do every other root disturbance as early as possible, is that onion roots are fragile. They grow down to 80cm at full extension and they’re thin and easily broken. When the roots get damaged, the plant reads it as a maturity signal and stops putting energy into bulbing. So you thin early, you weed early, and you do both when the soil is damp so the roots of nearby plants come out cleanly. This is not fussiness. It’s the mechanism that determines how big your onions get.

Plant out in the second week of May, 10cm apart with 30cm between rows. Don’t overfeed with nitrogen. It drives leaf growth at the expense of the bulb. Stop watering and feeding entirely in mid-July; this tells the plant to harden up and improves storage quality. You’ll know harvest is close when the foliage bends over at the neck.

Celeriac starts in February for a different reason: it takes 120 days to grow a worthwhile root, and that’s the minimum. Start in March and you’re harvesting in July, which is possible but premature, with small roots. Start in February and you’re harvesting from October through to the following March, which is when you actually want them.

Surface-sow celeriac on moist compost. Do not cover the seeds. They need light to germinate, and burying them is why most people get a patchy, erratic result. Water the compost thoroughly before sowing, then use a misting spray afterwards. Watering with a can after sowing washes the seeds around and gives you a cluster in one corner of the tray. 15-20°C. Two to three weeks to appear, sometimes longer. Keep at it.

Plant out in late May with fleece protection. An unexpected cold snap after planting can trigger bolting. Remove the lower leaves from July onwards to expose the swelling crown to light. Leave the plant in the ground all winter. Celeriac is fully frost-hardy and the root doesn’t deteriorate. Monarch and Prinz are the reliable varieties for UK growing. Celeriac is substantially easier than celery in UK conditions. It doesn’t need blanching, it doesn’t bolt as readily, and it stores in the ground for six months.

Cauliflower: what makes it harder than everything else

Cauliflower is the most demanding brassica, and the reason is buttoning. Buttoning is what happens when any growth check (drought, root-bound modules, loose soil, cold shock, transplant disturbance) tells the plant it’s in trouble. The plant reads that signal as maturity, stops growing normally, and throws up a tiny premature curd to try to set seed before conditions get worse. You end up with a head the size of a golf ball after twelve weeks of work. The solution to buttoning is not a fix. It’s not doing any of the things that cause it.

Sow in February for summer harvests from June onwards. Sow two seeds per 7cm module at 1cm depth. Germination temperature 15-20°C, 7-12 days. After germination, keep seedlings cool and bright at 10-15°C. Warmth produces leggy seedlings. Do not let the modules become root-bound. Transplant within 4-6 weeks of sowing, or pot on promptly if the weather prevents going out. Root-bound cauliflower seedlings are the most common cause of buttoning.

The soil needs to be rich, firm, and at pH 6.5-7.5. Dig in compost the autumn before and do not fork the bed again before planting. The soil needs to be firm enough that transplanted plants can anchor properly. Loose soil means roots can’t grip, plants rock in wind, roots break, and buttoning follows. Tread the bed before planting. Firm each plant in with your knuckles around the stem. Water immediately.

On infected ground, Clapton F1 is the only widely available clubroot-resistant variety. Clubroot persists in soil for twenty years. You can’t rotate away from it and you can’t treat it. Clapton F1 doesn’t eliminate the disease from the soil but it lets you grow brassicas where it would otherwise be impossible.

Summer varieties for February sowing: All Year Round is the most forgiving. The name is optimistic but it genuinely handles a wider range of conditions than most. Snowball is compact and quick, ideal for smaller plots. Clapton F1 for any ground with clubroot history. Once the curd starts to form, fold the outer leaves over and secure them. This keeps sunlight off the white curd and prevents it going yellow and bitter. Check daily. A cauliflower at its peak stays at its peak for about a week. After that the florets separate, the surface goes granular, and you’ve missed it.

Flowers: antirrhinums now, cosmos in March

Antirrhinums are a February flower because they’re slow. They’re technically short-lived perennials grown as half-hardy annuals in most UK gardens. Second-year plants go woody and flower poorly, so you sow fresh each season. A February sowing produces flowering plants from June through to the first hard frosts in October. That’s a long season. Wait until March and you lose six weeks of it.

The seeds are almost impossibly small. They need light to germinate, which means they go on the surface of moist compost, not under it. Water the compost thoroughly before sowing, not after, because watering after moves the seeds around and you end up with a cluster in one corner. Mist gently instead. 16-22°C. Cover the tray with clear plastic to hold moisture. Germination takes 7-21 days. Prick out when seedlings have 2-3 sets of true leaves, handling by a leaf and never the stem. Pinch out the growing tip when plants reach five or six leaves. This creates multiple stems and multiple flowering spikes instead of one.

Sweet peas should also be in by the end of February if they weren’t already done in January or October. The rules are the same as January: cool conditions, deep containers, nick the seed coat or soak overnight, pinch out at two pairs of true leaves.

Outdoor sowing in February: the honest assessment

In sheltered gardens in the mildest parts of the country (coastal south-west England primarily), you can sow broad beans and early peas under cloches in late February, and get away with hardy salad leaves and spinach in a protected spot. Everywhere else, wait until March. Soil below 5°C barely germinates anything. Seeds sitting in cold wet ground rot before they come up. March into warming soil gives you a cleaner, stronger result than February into cold mud.

The temptation to sow outside in February is understandable but the maths doesn’t support it. A seed that goes in two weeks later into better conditions overtakes one that went in early and then sat dormant for a fortnight.