If the current supermarket shortages of veg has inspired you to start growing your own, now is a great time to start, with aubergines, chilli peppers, sweet peppers and tomatoes. Ideally you’ll have access to a heated propagator, as they need temperatures of 18-25°C.
Don’t expect immediate results: they have small seeds, which make for small, slow-growing seedlings. Transplants will be at the ideal stage for planting out when the cold weather is past, in about 12 weeks, after growing on a bright window sill or in a frost-free greenhouse.
Delay sowing large-seeded crops such as courgettes, French beans, runner beans, pumpkins, squash, sunflowers and sweetcorn. These make big, lusty seedlings, reaching the right stage for planting out in six weeks – which is well before the risk of frost has passed. The seedlings continue growing, becoming big and lanky, and potentially spoil while waiting for warmer weather. Sow these instead in mid-late April, so they will be ready to transplant from late May.
Celery, celeriac, cucumbers and globe artichokes are intermediate. Celery and celeriac seeds are very small and are best sown indoors in early March. Globe artichokes have medium-sized seeds and are fairly hardy; mid-March suits them best. Cucumbers (and melons) are very tender, but the seeds are medium-sized – early April is ideal for unheated greenhouses and outdoor cultivation.
For outdoor sowing, the soil remains wetted by winter rains, while soil temperature is usually satisfactory around now, rising to 6°C or more for much of the time. Once weeds begin to germinate, crop seeds will grow too.
Outdoor sowing now suits hardy annual flowers and most vegetables, including broad beans, carrots, beetroot, bulb onions, kohlrabi, leeks, lettuces, parsnips, radish, peas, spinach, summer cabbage, salad leaves, summer cauliflower, Swiss chard, turnip and turnips. Garlic, onion and shallot sets can go in now, too.
Gardeners are naturally impatient, but delaying sowing when heavy rain or night frosts are forecast is wise.
Remember that later sowings, in the warmer days of April, often catch up earlier sowings made in poor conditions, especially where the soil is clay and in cooler regions.
When the soil dries enough to no longer stick to boots or tools, it can be raked to leave it in a crumbly, level state or “seedbed” into which seeds can be consistently sown at the right depth. Seedbeds made a few weeks in advance can be covered with clear polythene, coldframes or cloches to warm the soil before sowing aiding germination.
Covering newly sown areas with fleece or woven polythene will also warm up the soil, making sowing success more certain. Fleece, cloches or frames allow sowing, on average, two weeks before unprotected ground is ready.
Cloches and coldframes are a more environmentally favourable alternative to single-use plastic sheet materials and also do a better job, as they shed rain. They are more costly initially, but they last for at least five years and usually much longer.
Crops that most benefit from covering are those that need to be sown densely so that transplanting is laborious – broad beans, peas, salad onions and spinach, for example – or do poorly when transplanted – early carrots being an outstanding example.
Parsnips and maincrop carrots resent transplanting, too, but, having a long season of growth, can be sown uncovered in April, except for carrot fly-proof mesh, and will have all summer and autumn to bulk up for winter.
It is worth sowing some beetroot and turnips for the very earliest crops, as although they can be transplanted, direct sowing is usually better. Maincrop ones will grow readily when sown outdoors in April.
Lettuces, leeks, onions and all the cabbage tribe, including kohlrabi, are easily raised indoors as transplants. This also helps to avoid slug damage, especially if the transplants are grown to a larger size than usual, which can withstand some slug grazing after planting out.
Transplants are especially valuable for clay soils, which often do not dry out sufficiently for sowing until mid-April.
The easiest way to raise transplants is in module or cell trays. Natural rubber and paper trays are a sustainable alternative to plastic trays.
Transplants that are often planted out as large plants – courgettes, tomatoes and sweetcorn, for example – can be raised in small, 7-9cm pots. Biodegradable paper pots are highly suitable. Growing plants to a larger size than usual in module trays will ensure they form a dense rootball that will not disintegrate as you transplant into the ground. The larger plants will also tolerate some slug damage better than small seedlings.