Radish likes a well-drained fertile soil so add plenty of organic matter such as material from your compost bin. They also prefer a sunny spot on the plot and a moist soil, which is usually not a problem come autumn.
You can sow winter radish June to September direct on the plot in shallow drills about 1.5cm (½in) deep. Space rows about 30cm (12in) apart. The weather may be quite dry when you sow these so keep the ground watered and especially when the plants are still small.
When they emerge, thin out the seedlings to leave gaps between the plants. It can be done gradually as they continue to grow until the plants are about 10cm (4in) apart.