How to Grow Pumpkins and Winter Squash in a British Garden

There is a particular kind of optimism involved in growing pumpkins. You sow a seed barely bigger than your thumbnail sometime in April, tuck it into a pot on the windowsill, and within a few weeks you are harbouring something with genuine territorial ambitions. By August, if things go well, you will be negotiating with a plant that has colonised half the vegetable patch, smothered a nearby courgette, and is eyeing up the lawn. This is not a crop for the faint-hearted or the space-poor. But for those who can accommodate them, pumpkins and winter squash are among the most satisfying things a British kitchen gardener can grow, both for the table and for the sheer, unlikely pleasure of watching something so vast come from something so small.

Starting from Seed: April Under Glass

Sowing before mid-April gives you the longest possible growing season without the plants outgrowing their pots before the soil is warm enough outside. Squash are frost-tender and will sulk, stall, or simply die if planted out too early, so there is no benefit in rushing the sowing date much beyond the start of the month.

Sow each seed individually into a small pot, roughly nine centimetres, filled with peat-free multipurpose compost. Push the seed in on its side, about two centimetres deep. Sowing it flat rather than point-down reduces the risk of the seed rotting before it germinates. Keep the pots somewhere consistently warm, a propagator set to around 18 to 20 degrees Celsius works well, or a warm windowsill away from cold draughts. Germination is usually brisk, often within five to seven days, and the seedlings are unmistakably vigorous once they get going.

Once the first true leaves appear, move the plants somewhere bright. A south-facing windowsill is ideal. If light is limited, the seedlings stretch and weaken quickly, so do not leave them languishing in a dim corner of the kitchen out of convenience. From mid-May, begin hardening them off by setting the pots outside during mild days and bringing them back in before dusk.

Planting Out: Waiting for the Right Moment

Planting out before the last frost has passed is one of the more reliable ways to lose a squash plant. In Surrey and the wider South-East, that risk is generally past by late May, but further north or on exposed sites, waiting until early June is sensible. The soil temperature matters as much as the air temperature. Squash roots prefer the soil to be at least 12 degrees Celsius before they really settle in, and a cold soil after a warm spell is a common reason for transplants that sit sulking for weeks without putting on growth.

Choose the sunniest position available. Squash need warmth and light to ripen properly, and in a British summer, which rarely delivers either in abundance for as long as one might hope, every advantage counts. A sheltered south or south-west facing spot, ideally against a fence or wall that holds heat, will give you a head start.

Prepare the planting hole generously. Squash are hungry plants and will reward a good start: dig in a bucketful of well-rotted compost or manure before planting, and if your soil is heavy clay, work in some grit to improve drainage at the root zone. Plant at the same depth as the pot, firm in well, and water thoroughly. Spacing depends on the variety, but as a rule, allow at least a metre and a half between plants, and two metres if you are growing something truly vigorous like a 'Crown Prince' or an Atlantic Giant. This is not the moment for optimism about space.

Managing the Foliage

Once established, squash grow fast. By July you will be making decisions about what to do with the sprawling stems, and there are broadly two schools of thought. Some gardeners train the main stem in a wide loop or spiral to keep it contained within a defined area. Others simply let the plant wander and accept that it will go where it pleases, occasionally clearing a path when it heads somewhere inconvenient.

In my own garden, a combination of gentle redirection and resigned acceptance has served perfectly well. The stems can be pinched out once the plant has set two or three fruits, which directs the plant's energy into swelling those fruits rather than producing new growth that will never ripen before October. This is particularly worth doing from early August onwards, when the season is shortening and every calorie the plant produces needs to go into the fruits already on the vine.

Keep the plants well-watered through dry spells, particularly when the fruits are sizing up. Water at the base rather than over the foliage, which can encourage powdery mildew, a common affliction on squash in late summer and one that looks alarming but rarely kills an otherwise healthy plant. A weekly feed with a high-potash liquid fertiliser from late June onwards will support fruit development.

Knowing When to Harvest

Harvesting at the right moment is as important as anything that comes before it, and it is where many growers go wrong. A squash harvested too early lacks both flavour and keeping quality. Left on the vine through September and into October, the skins harden, the flesh deepens in flavour and sweetness, and the fruit will store well in a cool dry place for months rather than weeks.

The signs of readiness are reasonably clear once you know what to look for. The skin should be fully coloured and feel hard when you press it with a thumbnail. The stem should begin to dry and cork over at the point where it meets the fruit. In some varieties, the foliage dies back naturally at this point, which is the plant's own way of signalling that the work is done. Harvest with a generous length of stem intact, cutting cleanly, and then cure the fruits by leaving them somewhere warm and dry, a greenhouse or a sunny windowsill, for two to three weeks. This hardens the skin further and significantly improves keeping quality.

Varieties Worth the Space

This is where frank opinions are called for, because not all squash repay the considerable real estate they demand.

'Crown Prince' is, by most accounts, the best-flavoured winter squash available to British home growers. The skin is a distinctive blue-grey, the flesh is dense and deeply orange, and a single fruit will feed a family several times over. It stores brilliantly and improves with keeping. If you grow one winter squash, make it this one.

'Uchiki Kuri', also sold as Red Kuri or Onion Squash, is more compact than many varieties and well-suited to smaller gardens. The teardrop-shaped fruits are a vivid burnt orange and have a pleasantly nutty flavour with a smooth texture that needs no blending in soups.

'Butternut' is everywhere, and its familiarity is deserved. It is reliable, productive, and widely useful in the kitchen. The caveat is that it does need a warm summer to ripen fully outdoors in Britain, and in a poor year the fruits can be watery and underflavoured. In a good year, grown in a sunny sheltered spot, it is excellent.

For display rather than eating, 'Hundredweight' and the various Atlantic Giant varieties will produce fruits of extraordinary size, which is either a great achievement or a significant inconvenience depending on your storage situation and appetite. They are impressive on a doorstep in October, but the flavour is unremarkable and the flesh can be stringy. If you are growing for the table rather than for spectacle, give the plate varieties your space and your attention.

Heritage varieties are worth exploring through seed suppliers such as the Real Seed Catalogue or the Heritage Seed Library, which between them offer a range of squash with histories, flavours, and forms that the mainstream catalogues do not reach. 'Musquée de Provence', for instance, is a large, deeply ribbed French variety with rich, sweet flesh and an appearance that looks as though it has stepped directly from a seventeenth-century still life painting.

The Practical Reality of Storage

A successful squash harvest, particularly if you have grown several plants, quickly becomes a question of where on earth to put them all. They need cool, frost-free conditions with good air circulation, somewhere between 10 and 15 degrees Celsius. A spare bedroom, an unheated hallway, or a dry shed that does not freeze will all serve. Check them periodically through winter. Any fruit that shows soft spots or signs of rot should be used immediately, because rot spreads quickly from one fruit to another if they are in contact. Store them in a single layer if you can, with a little space between each.

If you are growing pumpkins and winter squash for the first time this season, the seed sowing window has already passed for this year, but it is never too early to plan for next. Note which varieties caught your eye, which catalogues you want to order from in January, and, perhaps most importantly, which corner of the garden might reasonably accommodate something that will, given half a chance, eat it entirely.