Depending on variety, radishes can usually be sown successionally from April until the end of July.

They've become so popular that 40 million packets were sold in the UK last year. If all the seeds grew to maturity, they'd weigh 8,000 tonnes and, laid end to end, the plants would form a line 6,000 miles long.

This versatile vegetable takes up very little space and can be intercropped between leeks or onions or beside peas or beans. Quick-growing radishes also give you a second crop on the same piece of ground.

Radishes are crammed with health-giving goodies. As well as containing antioxidants and anthocyanins, they are rich in the digestive enzyme diostase and aid digestion. They are a low GI food, so help stabilise blood sugar levels. Besides helping diabetics, their low calorie content is invaluable for slimmers. As a bonus, they take a fair bit of crunching, so can persuade your brain you're fuller than you actually are.

Garden centres and seed catalogues carry lots of varieties, with skins ranging from red or pink to white, yellow or black. The roots can be small and round or large and long, and the leaves make a tasty addition to any salad. Crisp, clean and spicy - what more could you want?

Radishes tolerate some abuse, but to avoid fibrous, foul-tasting roots that are a tough challenge for any dentures, follow a few simple rules. The ground should be fairly rich to provide a ready supply of nutrients for this quick-growing crop. Keep the soil well watered to avoid small fibrous specimens.

Whether you are sowing small summer radishes now or larger winter radishes in July, prepare the ground thoroughly. After digging in homemade compost, work the soil to a fine tilth, breaking down any lumps and removing stones. If possible, avoid using thin, gritty soil as it won't retain moisture. Equally, though, radishes don't thrive in clay soil because there's so little drainage.

First check the soil is warm enough; is your finger comfortable when sunk into the ground? If yes, start sowing. Use the edge of a rake or a hoe to draw out a row 1cm deep. Water this drill using a fine watering can rose. Sow seed thinly, 1cm apart. After around 10 days, thin the seedlings, leaving 3cm-5cm between summer radishes, 15cm for winter ones.

Keep the soil moist as the plants grow. Sow a few radishes every fortnight for regular cropping. During a really hot summer, radishes can bolt, so you may need to choose slightly shady places for any late May or June sowings. Use bolting-resistant varieties such as long, white Icicle or the new French Breakfast Francis.

Icicle is an unusually large summer radish, with 15cm roots. But such long roots are normal for winter varieties, such as Black Spanish Round or China Rose. As with all later sowings in Scotland, radish seed should be sown by mid July, when the soil is still warm and the sun is strong enough. If a seed packet tells you to sow in July or August, always choose July. If August or September, go for the former.

The best way to avoid winter radishes bolting, even with a July sowing, is to sow in Root Trainers and place them on a sunny window sill. When the seedlings have five leaves, transplant them into a sunny part of the garden. Provided the roots aren't disturbed, it's perfectly safe to treat radishes this way.

Because radishes are members of the brassica family, they are prone to attack from cabbage rootfly and radish flea beetle. To prevent this, cover the crop with fleece, just like carrots. But radish leaves are an important part of your harvest, so use cloche hoops or twigs to ensure the fabric doesn't touch the leaves.