Colza (Brassica napus)

Annual/Biennial
Common Name Latin Name Plant Family
Colza
Brassica napus
Cruciferae

The seed contains up to 45% of an edible semi-drying oil, it is used as a luminant, lubricant, in soap making etc[13, 21, 57, 142]. 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[269].

The seed husks are used in plastering house walls[272].

A good green manure, the deep taproot improves drainage and loosens heavy soils[18, 20, 87].

  • Medicinal Use

    The root is emollient and diuretic[240]. The juice of the roots is used in the treatment of chronic coughs and bronchial catarrh[240, 269].

    The seed, powdered, with salt is said to be a folk remedy for cancer[269].

    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[269]. It is dropped into the ear to relieve earaches[272].

  • Edible Use

    Leaves – raw or cooked[4, 34, 37]. Added to salads or used as a potherb[183, 272]. The leaves are also fermented for later use[272].

    Immature flowering stems – cooked in much the same way as broccoli[183].

    An edible oil is obtained from the seed, it is used mainly for cooking purposes, but can also be used raw in salad dressings[4, 13, 34, 46, 183]. Some caution is advised, however, see the notes above on toxicity.

    The sprouted seed is often used as the mustard part of mustard and cress. Eaten in salads[4, 34, 37, 183].

    The seed is used as a mustard flavouring[183].

  • Cautionary Notes

    The oil contained in the seed of some varieties of this species can be rich in erucic acid which is toxic. However, modern cultivars have been selected which are almost free of erucic acid.

Cultivation & Habitat

Seed – sow in situ in early spring to mid-August for a green manure crop.
Succeeds in full sun in a well-drained fertile preferably alkaline soil[200]. Succeeds in any reasonable soil[52]. Prefers a heavy soil and cool moist conditions[16, 20]. Sunny days and cool nights are favourable for plant growth whilst dry weather at harvest time is essential[269]. Colza is reported to tolerate an annual precipitation of 30 to 280cm, an annual average temperature range of 5 to 27¡C and a pH in the range of 4.2 to 8.2[269]. Very young plants are susceptible to cold damage, -4¡C either killing or injuring seedlings, whereas -2¡C has no affect when the plants are more than one month old[269]. Brassica napus is an aggregate species, probably derived through cultivation. It is thought that crosses of Brassica oleracea subsp. oleracea with B. rapa gave rise to the subsp. B. napus pabularia, from which subsp. napus and subsp. rapifera and other cvs were derived[269]. The aggregate species includes forms with swollen edible roots (B. napus napobrassica, the garden swede), forms grown for their oil-rich seeds (B. napus napus, the oilseed rape), forms grown for their edible leaves (B. napus pabularia, the rape kales) whilst the form grown as a green manure is B. napus arvensis. All these forms are treated separately here. 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[269]. The growth of this plant is inhibited by field mustard and hedge mustard growing nearby[18, 20]. This species is closely related to B. rapa[200].
Europe – Mediterranean. Naturalized in Britain[17].

Become ungovernable, break the chains of the matrix; grow and forage your own food and medicine.

*None of the information on this website qualifies as professional medical advice. Take only what resonates with your heart and use your own personal responsibility for what’s best for you. For more information [brackets] [000], see bibliography.