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Brassica napus ssp. oleifera

Cabbage Family [Brassicaceae]

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12th May 2010, Chesterfield Canal, Nottinghamshire. Photo: © RWD
Grows to 1.5m and grown as a crop for Rape-seed Oil. Difficult to walk through a planted field when fully grown. Shorter varieties are grown for less waste in harvesting the oil.

21st April 2005, Sankey Canal, nr St Helens. Photo: © RWD

21st May 2012, Alt Rifle Range, Freshfield, Sefton Coast. Photo: © RWD
Escapes everywhere. Here inside the grounds of an Army rifle range. Larger leaves lower down, and clasping the stem with auricles each side.

24th April 2005, Lancaster Canal, Lancs. Photo: © RWD
Almost spherical bunch of bright-yellow flowers atop, each with four petals.

16th Oct 2009, Blackleach Country Pk, Walkden, Gtr M/cr. Photo: © RWD
Some books say that the flower buds are slightly above the flowers, but this seems not to be always so. Upper leaves narrower and clasping the stem by auricles (here turned upwards for some reason).

16th Oct 2009, Blackleach Country Pk, Walkden, Gtr M/cr. Photo: © RWD
Sepals longish and narrow, with minute points at tip. Stem and leaves usually glaucous green.

16th Oct 2009, Blackleach Country Pk, Walkden, Gtr M/cr. Photo: © RWD
Seed-pods much longer than their stalks.

1st June 2014, Blackleach Country Pk, Walkden, Gtr M/cr. Photo: © RWD
Seed pods become slightly lumpy on the outside by their growing seeds within. seed pods topped by a thin long stalk (which can fall off).

21st May 2012, Alt Rifle Range, Freshfield, Sefton Coast. Photo: © RWD
Upper-leaf auricles clasping stem.

21st May 2012, Alt Rifle Range, Freshfield, Sefton Coast. Photo: © RWD
By transmitted light has few veins.

2nd July 2014, fields, Dyserth, North Wales. Photo: © RWD
Mature seed pods have broken and split-open releasing their seeds. Perhaps the farmer just abandoned this field full.

Easily mistaken for : Swede (Brassica napus ssp. rapifera) which otherwise looks identical but for the paler-yellow flowers.

Some similarities to : Tower Mustard (Turritis glabra) but this is very thin and tower-like, has upper leaves that are longer and thinner than those of Oil-seed Rape but which still half-clasp the stem with an auricle each side, and again the flowers are paler - pale-yellow to cream coloured.

Slight resemblance to : Gold-of-Pleasure (Camelina sativa) but the leaves are a pointed narrow arrow-shape but still half-clasping the stem. The flowers are yellow but the pods are short and oval rather than long and thin.

Superficial resemblance to : Winter-cresses such as Winter-cress (Barbarea vulgaris) but although these flowers are yellow and the leaves half-clasp the stem, the leaves are not entire but toothed (often with rounded teeth).

No relation to : Broomerapes such as Common Broomrape (Orobanche minor) [a plant with similar name].

The most dangerous time to walk through or near a field of Oil-seed Rape is during early summer when the flowers are shedding pollen, which to some susceptible folk is a dangerous allergen both from an asthma prospect and from a contact dermatitis aspect. Those seemingly un-affected by the pollen can nevertheless become sensitized to it through repeated exposure, as is the case with most antigens. But Oil-seed Rape pollen and dust is one of the worst offenders, not only because in the last 30 or 40 years it has become so widespread but because it is quite potent to some.

There are several sub-species of Brassica napus (previously called varieties):

  • Argentine Canola (Brassica napus ssp. napus)
  • Annual Rape (napus ssp. napus f. annua)
  • Turnip-Rape (Brassica napus ssp. oleifera)

Not to be confused with the similar sounding species Brassica rapa:

  • Wild Turnip (Brassica rapa ssp. capestris)
  • Swede (Brassica rapa ssp. rapifer)

And the hybrid between the two species:
Brassica × harmsiana (Brassica napus × Brassica rapa) - which can only be differentiated from either by its sterility or by its chromosome count (2n=29).

Oil-seed rape is a Hyperaccumulator of some toxic metals and has been planted in    Chernoble to help clear away contamination by radionuclides such as   Caesium-137, Cs137. It was found to be thrice as effective at this job than are other grain crops.

Oil-seed Rape is grown as a crop to harvest Rape Seed cooking oil obtained from the seeds in the pods. The cooking oil is slightly green in colour because it also contains chlorophyll. The exact composition of the oil varies because of production variabilities. Ordinarily it can contain large amounts (up to 60%) of the mono-unsaturated Omega-9 fatty acid called Erucic Acid which is poisonous in high concentrations damaging heart muscle. Some varieties of Brassica napus contain some toxic Glucosinolates, which convert to hydrocyanic acid within mammalian stomachs. But varieties of Brassica napus were bred so as to reduce the content of both of those toxins, they are called 'double-low' varieties ('00') for use as Rape-seed cooking Oil (called Canola Oil in America).

There are thus many cultivars grown which can escape and be mistaken for Brassica napus ssp. oleifera. Many of these are very variable in character in the wild, especially the leaves, and it is thought they may be reverting to the wild form. It is not known if any shown above are of these variants, or even if they all are!

There are 6 stamens with yellow anthers and one entire stigma.

Rape-seed Oil for human consumption contains the following oils in these approximate concentrations:
ω-9-Oleic Acid 60% (which replaces much of the Erucic Acid)
Linoleic Acid (ω-6) 20%
α-Linolenic Acid (ω-3) 10%
Palmitic Acid 5%
Stearic Acid 2%
Saturated Fatty Acids 9%
Trans Fatty Acids <1%

They do not sum to 100% because of overlap between some of the categories. But Rape-seed Oil is one of the most healthy oils to cook with that can also withstand higher cooking temperatures without degrading.

A variety called 'HO,LL Rape' meaning High Oleic acid and Low Linolenic acid, which contains no trans-fats, is used for industrial cooking oils.

'HEAR Rape' (High Erucic Acid Rape) is used industrially for bio-diesel and lubricating oils.

The residue of the seeds left over after crushing are used as animal feeds. 'Mustard and Cress' salad punnets are often made with Rape seedlings in place of White Mustard (Sinapis alba), which also has yellow flowers.

Small White


The Rape-seed oil used for fuel can contain much higher amounts of Erucic Acid and other toxins without any detriment. Its quantity in cooking oil is reduced to much lower levels. It has a much higher concentration in the seeds of Kale (a variety of Brassica oleraceae).

Chemically it is a cis-mono-unsaturated ω-9 fatty acid and is otherwise known as cis-docosenoic Acid. The trans-form is known as Brassidic Acid. Present also in the seeds of Wall-Flower (Erysimum cheiri) and many other plants belonging to the Brassica genus.

It is not very poisonous, but nevertheless is an unwanted constituent of Rape-seed Oil and efforts are made to reduce the daily intake of Erucic Acid to less than 500mg/day, giving a safety margin of 120-fold (as measured in their myocardial lipidosis effects on nursling pigs; human experiments have not been done for ethical reasons). Thus its concentration in food-grade Rape-seed Oil is kept below 2%.


Oil-seed Rape contains several steroidal compounds, the dominant being Sitosterol followed by Campesterol with significant amounts of others such as Cholesterol, Brassicasterol and 5-Avenasterol, with environmental factors such as temperature, rainfall, fertiliser application affecting both fatty acid and steroidal content.

Brassinolide looks similar to a steroidal compound, but actually on closer examination has a 7-membered lactone ring in place of a 6-membered carbon ring. This was first isolated from the pollen from Oil-seed Rape and it turns out to be a plant hormone or Auxin capable of enhancing the growth of Oil-seed Rape (by this means, and possibly by others, once established, Oil-seed Rape is able to block out all competitors).

δ-5-Avenasterol is another steroidal compound present in Oil-seed Rape and is shown for completeness; your Author knows nowt about it except that it has an ethylidene side-chain (top-most).

  Brassica napus ssp. oleifera  ⇐ Global Aspect ⇒ Brassicaceae  

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Brassica napus ssp. oleifera

Cabbage Family [Brassicaceae]