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[].

Common Name: Colza

General Information

Brassica napus is an erect to spreading, annual to biennial plant; branched above, it can grow from 30 - 150cm tall[].
Brassica napus is an aggregate species, derived in cultivation. It has three commonly cultivated forms, one supplying an edible root, another edible leaves and the third is a major source of oil for food and industry. Each form has a separate record.
A widely cultivated plant, it sometimes escapes from cultivation and becomes established - it has been described as invasive in countries such as New Zealand and the Galapagos Islands of Ecuador[].

Known Hazards

The oil contained in the seed of some varieties of this species can be rich in erucic acid which is used in industry but is toxic if consumed. However, modern cultivars have been selected for culinary use which are almost free of erucic acid[].

Botanical References

Range

A much cultivated plant, possibly originationg from the Mediterranean region, though this is not clear and it might have arisen in cultivation

Habitat

Banks of streams, ditches and arable fields in Britain[].

Properties

Edibility Rating
Medicinal Rating
Habit	Annual/Biennial
Height	1.20 m
Pollinators	Bees, Self
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Brassica napus is a plant of the temperate zone, much cultivated in temperate regions and also in the subtropics and sometimes at higher elevations in the tropics.
Succeeds in full sun in a well-drained fertile preferably alkaline soil[]. Succeeds in any reasonable soil[]. Prefers a heavy soil and cool moist conditions[, ]. Sunny days and cool nights are favourable for plant growth whilst dry weather at harvest time is essential[]. Colza is reported to tolerate a pH in the range of 4.2 to 8.2[].
Brassica napus is an aggregate species, probably derived through cultivation. It is thought that crosses of Brassica oleracea with Brassica rapa gave rise to the subspecies Brassica napus pabularia, from which the subspecies napus and rapifera and other cvs were derived[]. Theere are individual records for all the following forms:-
Brassica napus subsp napus. The oilseed rapes, sometimes further subdivided into spring-sown and autumn-sown forms.
Brassica napus subsp rapifera. Rutabaga or Swede. Often grown commercially and in gardens for its edible swollen root.
Brassica napus subsp pabularia. Rape kale or Siberian kale. Cultivated as a vegetable for its leaves.
The oil obtained from the seed is high in erucic acid and glucosinolates, both of which have anti-nutritional properties. Cultivars have been developed that have a low content of these items and are therefore suitable for food.
Colza is 70% self-pollinating and 30% cross-pollinated. Even if wind and insects are absent, seed are still produced. Yield increases with honeybees[].
This species is closely related to Brassica rapa[].

Edible Uses

Leaves - raw or cooked[, , ]. Added to salads or used as a potherb[, ]. The leaves are also fermented for later use[].

Immature flowering stems - cooked in much the same way as broccoli[].

An edible oil is obtained from the seed, it is used mainly for cooking purposes, but can also be used raw in salad dressings[, , , , ]. Some caution is advised, however, see the notes above on toxicity.

The seed is used as a mustard flavouring[].
The sprouted seed is often used as the mustard part of mustard and cress. Eaten in salads[, , , ].

Medicinal

The root is emollient and diuretic[]. The juice of the roots is used in the treatment of chronic coughs and bronchial catarrh[, ].

The seed, powdered, with salt is said to be a folk remedy for cancer[].

Rape oil is used in massage and oil baths, it is believed to strengthen the skin and keep it cool and healthy. With camphor it is applied as a remedy for rheumatism and stiff joints[]. It is dropped into the ear to relieve earaches[].

Agroforestry Uses:

A good green manure, the deep taproot improves drainage and loosens heavy soils[, , ].
The growth of this plant is inhibited by field mustard and hedge mustard growing nearby[, ].

Other Uses

The seed contains up to 45% of an edible semi-drying oil, it is used as a luminant, lubricant, in soap making etc[, , , ]. Rapeseed oil has potential market in detergent lubrication oils, emulsifying agents, polyamide fibres, and resins, and as a vegetable wax substitute. According to the Chemical Marketing Reporter (April 26, 1982) 'the most common use for the oil is still in the production or erucic acid, a fatty acid used in turn in the manufacture of other chemicals[].

The seed husks are used in plastering house walls[].

Propagation

Seed - sow in situ in early spring to mid-August for a green manure crop.