This species has been cultivated as a food crop for many hundreds of years and, in that time, several quite distinct forms have arisen. The nomenclature of these forms is confused, to say the least, and by no means universally accepted. We have followed the treatment used by GRIN, though it is very likely to be revised in the future[
Barbarea derchiensis S.S.Ying
Brassica campestris rapa (L.) Hook.f.
Brassica campestris rapifera (Metzg.) Sinskaya
Brassica rapa rapifera Metzg.
Raphanus rapa (L.) Crantz
Common Name: Turnip
The turnip is a biennial plant developed in cultivation from wild forms of Brassica rapa. Growing from a fleshy taproot, it forms a loose cluster of leaves 30 - 50cm tall and, in its second year of growth, a flowering stem up to 100cm tall[
Turnips are widely grown, both on a commercial scale and in gardens, for their edible roots.
Derived in cultivation
Not known in the wild.
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The turnip arose through cultivation in the temperate zone. Basically a cool climate crop that is resistant to frost and mild freezes, it can also be cultivated at higher elevations in the tropics and subtropics[
]. It grows best in areas where annual daytime temperatures are within the range 10 - 17°c, but can tolerate 7 - 30°c[
]. When dormant, the plant can survive temperatures down to about -10°c, but young growth can be severely damaged at -4°c[
]. It prefers a mean annual rainfall in the range 900 - 1,400mm, but tolerates 300 - 2,000mm[
Turnips are very easily grown, provided they grow quickly when young and the soil is not allowed to dry out[
]. They succeed in full sun in a well-drained fertile preferably alkaline soil[
]. They grow best in a deep, friable, highly fertile soil with a pH in the range 5.5 - 6.8, though they can tolerate 4.3 - 7.5[
]. They are said to prefer a light sandy soil, especially when grown for an early crop in the spring, and dislike a heavy soil[
]. They prefer cool moist growing conditions[
A fast growing plant, it can take less than ten weeks from sowing to harvesting[
]. Its short growing season makes it very adaptable as a catch crop[
Yields are normally between 20- 25 tonnes per hectare[
In biomass trials, 2,000 - 2,500 litres of ethanol have been obtained from a hectare[
There are several named varieties and by careful selection and successional sowing it is possible to harvest roots all year round.
The roots are fairly cold hardy and can be left in the ground during the winter, harvesting them as required. However, they can be troubled by slugs and other creatures so it is often better to harvest them in late autumn or early winter and store them in a cool but frost-free place.
Brassica rapa has long been cultivated as an edible plant and a large number of diverse forms have been developed. Botanists have divided these forms into a number of groups, and these are detailed below. Separate entries in the database have been made for each group.
Brassica rapa. The species was actually named for the cultivated garden turnip with its edible swollen tap root. This form is dealt with on this record.
Brassica rapa chinensis. Pak choi has long been cultivated in the Orient for its large tender edible leaves which are mainly produced in the summer and autumn.
Brassica rapa dichotoma. Cultivated in the Orient mainly for its oil-rich seeds.
Brassica rapa narinosa. Chinese savoy is another Oriental form. It is grown for its edible leaves.
Brassica rapa nipposinica. Mizuna is a fast-growing cold-hardy form with tender edible leaves that can be produced all year round.
Brassica rapa oleifera. The stubble turnip has a swollen edible root, though it is considered too coarse for human consumption and is grown mainly for fodder and as a green manure. It is also cultivated for its oil-rich seeds.
Brassica rapa parachinensis. False pak choi is very similar to Brassica rapa chinensis with tender edible leaves, though it is considerably more cold-hardy.
Brassica rapa pekinensis. Chinese cabbages are widely grown in the Orient. The large tender leaves often form a cabbage-like head.
Brassica rapa perviridis. Spinach mustard is grown for its edible leaves. A very cold-hardy plant, and also able to withstand summer heat, it can provide a crop all year round.
Brassica rapa trilocularis. Indian colza is mainly grown for its oil-rich seeds.
A good bee plant[
Root - raw or cooked[
]. Often used as a cooked vegetable, the young roots can also be grated and eaten in salads, they have a slightly hot flavour like a mild radish. A nutritional analysis is available[
Leaves - raw or cooked[
]. The cooked leaves make an acceptable vegetable, though they are coarser than the related cabbage. They are more often used as a spring greens, sowing the plants in the autumn and allowing them t overwinter. Young leaves can also be added in small quantities to salads, they have a slightly hot cabbage-like flavour and some people find them indigestible[
]. A nutritional analysis is available[
A decoction of the leaves or stems is used in the treatment of cancer[
The powdered seed is said to be a folk remedy for cancer[
]. The crushed ripe seeds are used as a poultice on burns[
]. Some caution should be exercised here since the seed of most brassicas is rubefacient[
The root when boiled with lard is used for treating breast tumours[
A salve derived from the flowers is said to help treat skin cancer[
Grows well with peas but dislikes growing with hedge mustard and knotweed[
Turnip root peelings contain a natural insecticide. The chopped roots can be brewed into a tea with flaked soap, this is then strained before use. It is effective against aphids, red spider mites and flies[
The starch from the roots is a source of biomass, used for producing bio-ethanol[
Seed - sow in situ from early spring to late summer. The first sowing can be made under cloches in late winter and will be ready for use in early summer. The latest sowings for winter use can be made in mid to late summer.