How to Grow Turnips
This biennial ‘root’ vegetable — it is mainly swollen hypocotyl (the zone between the true root and the seed leaves or cotyledons) — has been known since prehistoric times. It is grown primarily for the faintly-flavoured ‘root’ which normally has white flesh.
The usual time of use is in the winter but cultivars are available which produce young, tender roots during the summer. The very earliest summer crops are raised under frames or cloches. Roots which are left in the ground over the winter will re-grow in the spring and the new young tops can be eaten as ‘spring greens’.
Soil and fertilizer requirements
Fertile, well-drained and yet moisture retentive soils are ideal for. Summer crops particularly must grow rapidly to produce tender roots and they can, therefore, be grown as catch crops. Don’t grow turnips on which has been freshly manured as the roots will be mis-shapen. Fertilizers for turnips should be low in nitrogen and rich in phosphates. Too much nitrogen for summer crops usually results in excessive leaf growth at the expense of the ‘roots’ while winter crops will also be less hardy if they are soft.
Seed sowing and crop management
Make the earliest sowings under protection in February, using special short-top forcing cultivars. Mark out the seedbed into a network of 12-cm (5-in) squares. At the points where the lines cross sow 3 or 4 seeds in 1 to 2-cm (about 1-in) deep holes. Cover the seeds over and thoroughly soak the seedbed before covering with the frames or cloches. When theemerge, thin to one at each station. Water generously as required and give full ventilation on warm, sunny days. If the turnips are grown rapidly the leaves will quickly cover the ground and will not be a problem.
Outdoor summer crops can be sown from March onwards in 2-cm (1-in) deep drills which are 30cm (12in) apart. Thin the seedlings to 15cm (6in) apart as soon as possible.
Winter turnips are grown from sowings made from mid-July until mid-August. These larger rooted types should be grown at 30cm (12in) or even 40cm (16in) square.
Pull summer turnips once they reach 5 to 8cm (2 to 3in) in diameter which should be in May from March sowings. Any delay in pulling mature roots will cause the loss of the crisp texture and flavour. Winter turnips are lifted as needed.
Pests and diseases
Turnips and swedes not only suffer from some of thewhich attack other brassicas, but also from some of the problems of root crops. Consequently flea beetle damage may occur on the young seedlings while club root, damping-off and downy mildew can also cause trouble. Discoloured areas within the roots are often due to boron deficiency while root splitting is caused by fluctuating water supplies. Violet root rot fungus appears as purple threads in and on the roots whereas soft bacterial rots cause damaged or badly stored roots to break down into a watery, evil-smelling mass.
There is considerable variation in the ‘root’ form of cultivated turnips. Some are round, others flattened; many are white-skinned but others are yellow and either may have a green or purple shoulder.
Summer crops ‘Tokyo Cross’: F1—quick growing; globe shaped; pure white. ‘Early Snowball’: sweet flavoured globular roots. ‘Jersey Navet’: white cylindrical roots; forcing type.
Winter crops ‘Golden Ball’: very hardy with yellow skin and flesh. ‘Green-top white’: half green, half white roots with white flesh. ‘Manchester Market’: good, winter-hardy.