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Brassica napus - L.

Colza

Author	L.	Botanical references	200
Family	Cruciferae	Genus	Brassica
Synonyms
Known Hazards	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.
Range	Europe - Mediterranean. Naturalized in Britain[17].
Habitat	Banks of streams, ditches and arable fields in Britain[17].
Edibility Rating	3 (1-5)	Medicinal Rating	2 (1-5)

Physical Characteristics

Annual/Biennial growing to 1.2m.

The plant prefers light (sandy), medium (loamy) and heavy (clay) soils, requires well-drained soil and can grow in heavy clay soil. The plant prefers acid, neutral and basic (alkaline) soils and can grow in very acid and very alkaline soils. It can grow in semi-shade (light woodland) or no shade. It requires moist soil.

Habitats

Cultivated Beds;

Edible Uses

Edible Parts: Leaves; Seed; Stem.

Edible Uses: Condiment; Oil.

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].

Medicinal Uses

Diuretic; Emollient.

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].

Other Uses

Green manure; Oil.

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].

Cultivation details

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].

Propagation

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

Cultivars

No entries have been made for this species as yet.

Links

This plant is also mentioned in the following PFAF articles: Alternative Lighting: Plant Oils and Waxes.

Permaculture.info Details of this plant in the Permaculture.info project, a community plant and permaculture database.

References

[4] Grieve. A Modern Herbal. Penguin 1984 ISBN 0-14-046-440-9
Not so modern (1930's?) but lots of information, mainly temperate plants.

[13] Triska. Dr. Hamlyn Encyclopaedia of Plants. Hamlyn 1975 ISBN 0-600-33545-3
Very interesting reading, giving some details of plant uses and quite a lot of folk-lore.

[16] Simons. New Vegetable Growers Handbook. Penguin 1977 ISBN 0-14-046-050-0
A good guide to growing vegetables in temperate areas, not entirely organic.

[17] Clapham, Tootin and Warburg. Flora of the British Isles. Cambridge University Press 1962
A very comprehensive flora, the standard reference book but it has no pictures.

[18] Philbrick H. and Gregg R. B. Companion Plants. Watkins 1979
Details of beneficial and antagonistic relationships between neighbouring plants.

[20] Riotte. L. Companion Planting for Successful Gardening. Garden Way, Vermont, USA. 1978 ISBN 0-88266-064-0
Fairly good.

[21] Lust. J. The Herb Book. Bantam books 1983 ISBN 0-553-23827-2
Lots of information tightly crammed into a fairly small book.

[34] Harrison. S. Wallis. M. Masefield. G. The Oxford Book of Food Plants. Oxford University Press 1975
Good drawings of some of the more common food plants from around the world. Not much information though.

[37] Thompson. B. The Gardener's Assistant. Blackie and Son. 1878
Excellent general but extensive guide to gardening practices in the 19th century. A very good section on fruits and vegetables with many little known species.

[46] Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959
An excellent and very comprehensive guide but it only gives very short descriptions of the uses without any details of how to utilize the plants. Not for the casual reader.

[52] Larkcom. J. Salads all the Year Round. Hamlyn 1980
A good and comprehensive guide to temperate salad plants, with full organic details of cultivation.

[57] Schery. R. W. Plants for Man. 0
Fairly readable but not very comprehensive. Deals with plants from around the world.

[87] Woodward. L. Burge. P. Green Manures. Elm Farm Research Centre. 1982
Green manure crops for temperate areas. Quite a lot of information on a number of species.

[142] Brouk. B. Plants Consumed by Man. Academic Press 1975 ISBN 0-12-136450-x
Readable but not very comprehensive.

[183] Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990 ISBN 0-9628087-0-9
Excellent. Contains a very wide range of conventional and unconventional food plants (including tropical) and where they can be obtained (mainly N. American nurseries but also research institutes and a lot of other nurseries from around the world.

[200] Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992 ISBN 0-333-47494-5
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.

[240] Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement). Council of Scientific and Industrial Research, New Delhi. 1986
Very terse details of medicinal uses of plants with a wide range of references and details of research into the plants chemistry. Not for the casual reader.

[269] Duke. J. Handbook of Energy Crops - 1983
Published only on the Internet, excellent information on a wide range of plants.

[272] Manandhar. N. P. Plants and People of Nepal Timber Press. Oregon. 2002 ISBN 0-88192-527-6
Excellent book, covering over 1,500 species of useful plants from Nepal together with information on the geography and peoples of Nepal. Good descriptions of the plants with terse notes on their uses.

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