This Brassica napus genus contains a couple of other plants as well,
Edible Parts: Leaves; Root.
Leaves - cooked as a potherb. A mild, cabbage-like flavour to a spicy flavour. Root - swede, perhaps others as well - raw or cooked. A sweeter 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.
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.
The seed contains up to 45% of an edible semi-drying oil, it is used as a luminant, lubricant, in soap making etc.
Succeeds in full sun in a well-drained fertile preferably alkaline soil. Prefers a light but rich soil and a fairly high rainfall and an open sunny position. Succeeds in any reasonable soil. Sunny days and cool nights are favourable for plant growth whilst dry weather at harvest time is essential. 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. The plant is somewhat hardier than turnips. Plants take 4 - 6 weeks longer to mature than turnips. Swede is 70% self-pollinating and 30% cross-pollinated. Even if wind and insects are absent, seed are still produced. Yield increases with honeybees. A good companion plant for peas but it dislikes growing with hedge mustard and knotweed.