Squash club: May is the time to sow your crops – and pumpkins and squash are the best of the lot

May is mayhem for vegetable growers. So much stuff needs to be sown, including the crops that will keep you going through autumn and winter: beetroot, autumn and winter cabbage, calabrese, carrots, cauliflower, chicory, kale, salsify, scorzonera, turnips and the best of them all – pumpkins and squashes. "Squash never fail to reach maturity," wrote the American humorist S J Perelman. "You can spray them with acid, beat them with sticks and burn them; they love it." That kind of dogged determination is an endearing characteristic in a plant. Since you will have to work hard to prevent squashes and pumpkins from growing, you can divert your energy to the question of choice. Which members of this staggeringly varied family – apricot, orange, yellow, green, ivory, or a mesmeric metallic pewter grey – would you most like to look at this summer?

Choice becomes easier if you divide the family into three different categories. Summer squashes, which include the flat, frilled patty pans, do not store well. Winter squashes such as the beautiful, polished blue-green 'Crown Prince' should store right through the winter if the skins are well cured. Pumpkins, which include 'Dill's Atlantic Giant' – at 456kg the world's heaviest vegetable – will also keep if they are allowed to ripen fully on the vine before they are picked.

Some of the larger pumpkins have the lopsided look of quietly deflating beach balls. Others, like the warty blue 'New England Blue' bulge intemperately in the middle, tapering off either end like a balloon that won't blow up (there is one in every pack). 'Marina di Chiogga', striped in grey and sage green, looks just like the streetwise headgear worn by the Capulet gang in Romeo and Juliet. Others are avant garde artworks, customised in patches of apricot and husk-coloured beige.

In essence, growing a pumpkin or squash is much like growing a marrow or courgette. All are members of the same big group, the cucurbits, but some types, such as the Cucurbita moschata varieties 'Butternut' and 'Harrier', like more heat than others. As with courgettes, you can't put the plants outside until the end of May when temperatures begin to rise.

You can start seeds off now in pots inside, either on a windowsill or in a greenhouse, setting a single seed on its edge in a 7cm pot of compost. Cover the pots with clingfilm and keep them at a temperature of 60-65F until the seeds have germinated. This should take no more than a week. The trick is not to get the compost too wet. If you do, the seeds rot.

Later this month, in sheltered spots, you can also sow direct into the ground, setting a jam jar over each seed both to act as a mini-greenhouse and to protect them from mice. Choose an open, sunny site in ground that is rich, well fed but also well-drained. Pumpkins and squashes grow most happily where the soil is slightly acid to neutral. Set the plants at least a metre apart and away from less robust crops which they may smother.

Most pumpkins and squashes grow on big, trailing stems that may be more than 5 metres long; the well-flavoured pumpkin 'Jack be Little' grows on a more compact plant. In a small plot, the modest fruits of cultivars such as 'Sweet Lightning' (Organic Gardening Catalogue £1.58), the patty pan squash 'Sunburst' (Suffolk Herbs £1) or the compact trailing 'Rolet-Gem' (Edwin Tucker £1.20) which has apple-sized fruits with buttery, firm flesh, will be easier to accommodate than 'Atlantic Giant', a pumpkin that is big enough to take Cinderella to the ball. You can train them over arbours, arches or wigwams of wooden poles, but choose types with smallish fruit. No wigwam will be able to stand the weight of an 'Atlantic Giant' with the bit between its teeth.

Some cultivars, such as 'Sunburst' (Edwin Tucker £1.30), a very productive, bright-yellow patty pan squash, and various other scallop and crookneck squashes should be eaten as soon as they have developed in summer. Winter squash and Halloween pumpkins mature more slowly and need to be "cured" in the sun to harden their skins if they are to store successfully under cover through the winter. I especially like the nutty-tasting 'Uchiki Kuri' (Edwin Tucker £1.30) which has pear-shaped fruit ripening to dark orange. Delfland Nurseries can supply organically grown young plants of this variety for delivery in late May (£1.70 for three plants plus postage and packing).

Once planted, most of this tribe can be left to their own devices. They will easily smother weeds and their leaves shade the earth so that it does not dry out as quickly as open ground. Butternut squashes sometimes grow masses of leaf and stem but are reluctant to set fruit. Curb this tendency by pinching out the growing tips of the shoots when they've got to about 120cm. Butternuts, which do much of their growing at the end of summer, need a long, warm autumn to produce decent fruit. In the States, you see young plants sitting in the middle of low stockades of mounded up earth, each circle about a metre across. The low earth walls stop water running off in all directions when you empty a can over a plant.

In the States too, you often see pumpkins and squashes grown in conjunction with sweetcorn, the long trailing growths winding their way through the tall stems of the corn. This is an economical way to use ground and the combination looks good too. Tomatoes, securely staked, would make an equally good companion crop. Both need sun.

Given the right conditions, pumpkins, once set, fatten up prodigiously fast. They can put on half a kilo a day without even thinking about it, a weight watcher's nightmare, a champion vegetable grower's dream. The yield will depend on the type of pumpkin or squash you are growing. The little scallopinis or patty pans such as the super-productive 'Sunburst' or 'Yellow Bird' (available as plantlets – 6 for £7.50 from Simpsons Seeds) should be cut when they are no more than 13cm across. Cut the summer squashes to use as you need them. Dry off the winter pumpkins until the skins are hard and the fruit sounds hollow when you tap it. Store pumpkins and squashes in a cool, frost-free shed until you need them.

An old book I have says rather intriguingly that young shoots of pumpkin, gathered in summer, are an excellent substitute for asparagus. I've never tried that, but I have successfully toasted seeds scraped from the innards. Clean the seeds off in a sieve under a running tap, let them dry and then spread them out on a baking sheet. Sprinkle them lightly with salt and bake them for about 20 mins at 190C/375F/gas mark 5.

Seed of a wide range of pumpkins and squashes is available from the Organic Gardening Catalogue, Riverdene, Molesey Rd, Hersham, Surrey KT12 4RG, 0845 130 1304, organiccatalogue.com; Simpson's Seeds, The Walled Garden Nursery, Horningsham, Warminster, Wiltshire BA12 7NQ, 01985 845004, simpsonsseeds.co.uk; Suffolk Herbs, Monks Farm, Coggeshall Rd, Kelvedon, Essex CO5 9PG, 01376 572456, suffolkherbs.com; Delfland Nurseries Ltd, Benwick Rd, Doddington, March, Cambs PE15 0TU, 01354 740553, organicplants.co.uk; Edwin Tucker & Sons Ltd, Brewery Meadow, Stonepark, Ashburton, Devon TQ13 7DG, 01364 652233, edwintucker.com. From Edwin Tucker you can also order 'The Squash: History, Folklore & Ancient Recipes' (£9.99)