How to grow Turnip plant from seed
This root vegetable, Brassica campestris rapa (syn. B. rapa), has been grown in Britain since the sixteenth century. The roots are global or flattish round. A well-drained sandy loam is suitable for both types—summer and winter. But if the soil is light and sandy, it dries out rapidly and turnip flea beetles flourish. A heavy soil is unsuitable for summer turnips but is usually suitable for the winter type. Both very light and heavy soils are improved by regular winter dressings of manure, etc. A site that was manured for a previous crop should be chosen. If liming was not carried out during the previous winter, ground chalk should be dusted on to the surface at the rate of 110g (4oz) to the sq m (sq yd) before seed sowing.
The first sowing, out of doors or under cloches, may be made from mid-March to mid-April with a second successional sowing in May. Sow seed thinly 1cm (0.5in) deep in rows 30cm (1ft) apart. Dust seedlings with derris to control flea beetles and hoe to keep down weeds. Thin the seedlings to 10cm (4in) or so apart and water in dry spells. Quick growth with no checks at all is essential for succulent summer turnips. Start pulling for use when the turnips are sufficiently large. If left to age they become coarse and fibrous. Sow seed of winter turnips similarly, in late July or early August. Water seed drills if the soil is dry and sow after the water has drained away. Dust the seedlings with derris and thin to 23cm (9in) apart. Winter turnips are often left in the ground and pulled when wanted. In colder parts the roots are best lifted in the autumn when the outer leaves are yellowing. Cut back the foliage to about 1cm (0.5in) from the crown and shorten long tap roots by 10cm (4in) before storing the roots in moist sand or ashes.
For a supply of turnip tops for 'greens' in spring sow seed of a suitable variety in August quite thickly in 1cm (0.5in) deep drills spaced at 46cm (18in) apart. In colder areas the plants benefit from cloche protection during the winter.
When picking leaves for use take but one or two from each plant.
Turnip varieties Summer 'Early Snowball', 'Early White Milan', 'Red Top Milan" 'Golden Ball' ; winter 'Manchester Market' ; for turnip tops 'Hardy Green Round', 'Green Globe'.