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: Swede

General Information

Brassica napus rapifera is a biennial plant with a swollen, edible root. The plant grows around 30cm tall in its first year of growth, sending up a flowering stem up to 1 metre tal in its sedond year.
The garden swede is often cultivated, both in gardens and commercially, for its edible root.

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 hybrid of garden origin between B. napus and B. campestris.

Habitat

Not known in the wild.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Biennial
Height	0.75 m
Pollinators	Bees, Self
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

The swede is much cultivated in the temperate to subtropical zones. It grows best in areas where annual daytime temperatures are within the range 14 - 24°c, but can tolerate 5 - 35°c[]. When dormant, the plant can survive temperatures down to several degrees below freezing, but young growth can be severely damaged at -1°c[]. 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[]. It prefers a mean annual rainfall in the range 700 - 1,000mm, but tolerates 300 - 2,800mm[, ].
Succeeds in full sun in a well-drained fertile preferably alkaline soil[, ]. Prefers a stiff moist soil and a fairly high rainfall[, , ]. Another report says that it prefers a light but rich soil and an open sunny position[]. Succeeds in any reasonable soil[]. Sunny days and cool nights are favourable for plant growth[]. Prefers a pH in the range 5.5 - 7, tolerating 4.2 - 8.2[, ].
There are several named varieties[].
Plants take around 180 days from sowing to first harvest of the mature roots, generally 4 - 6 weeks longer to mature than turnips[, ].
The plant is somewhat hardier than turnips and in much of the temperate zone the roots can usually be left outdoors all winter and harvested as required, though in cold winter areas it would be safer to harvest the roots and store them.
Swede is 70% self-pollinating and 30% cross-pollinated. Even if wind and insects are absent, seed are still produced. Seed yield increases when honeybees fertilize the flowers[].

Edible Uses

Root - raw or cooked[, , , , ]. A richer flavour than turnips, it makes a good cooked vegetable and, when finely grated, is acceptable in mixed salads[, ]. The root can be 30cm or more in diameter, though it is usually eaten smaller since it then is more tender[]. It is available from early autumn, and can either be left in the ground over winter to be harvested as required, or can be harvested and stored in a cool, frost-free place where it will keep for 6 months[].

Leaves - cooked as a potherb[]. A mild, cabbage-like flavour[].

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 companion plant for peas but it dislikes growing with hedge mustard and knotweed[].

Other Uses

The seed contains up to 45% of an edible semi-drying oil. Since it is grown as a root crop, the plant does not normally get utilized for its seeds. When available, it can be used as a luminant, lubricant, in soap making etc[, , , ]. It is probably best not to use it for food - see the notes above on toxicity[].

Propagation

Seed - sow mid spring to early summer in situ.