These purple-topped and white-bottomed summer radishes provide an attractive splash of colour to the vegetable garden. Olive-shaped, peppery roots are ready to harvest from just 25 days after sowing. Sow successionally outdoors from March to September or in pots under glass to prolong the season.Sow thinly in broad drills, 1cm (½in) deep, 30cm (12in) apart in soil which has been raked to a fine tilth. Water ground regularly, especially during dry periods.Thin as necessary, allowing 2.5cm (1in) between seedlings and keep watered to prevent bolting (running to seed) and a harvest of hot, pithy roots.