Sow radishes every ten days

Good advice in spring and summer to ensure a continuous supply of this ever popular salad vegetable. Summer radishes are easy to grow, and are best sown in small quantities since, once mature, they quickly become woody. Two rows side by side, each about 1 m (39 in) long is ample at each sowing. The soil need not be deeply dug, but should not be recently manured. Classic summer varieties, including the old white-tipped favourite  ‘French Breakfast’ and can be started under cloches, or even outdoors in a sunny spot as early as January.
Winter radishes, with long or turnip-shaped roots that can weigh up to 250 g (8oz) and more, need soil that is more deeply dug and take longer to mature. Seed sowing is from June to August. It is now also easy to obtain seeds of the white Japanese radish – known as the daikon or mooli – hybridized for garden excellence and mild, peppery flavour.
According to the Greek historian Herodotus the Great Pyramid of Egypt bears an inscription of the vast quantities of radishes (and onions and garlic) eaten by the slaves who worked on its construction.

Taken from the book The Gardener's Wise Words and Country Ways.