Root rod, spindle-shaped, reinforced in the top part, branched. The main part of branched roots is concentrated on depth of 20 — 45 cm, but by the period of maturing of seeds can extend also in the horizontal direction. Root thickness to 3 cm, it gets into the soil to 3 m at colza and winter and to 2 m at summer.
The stalk is upright, roundish, branched out with 12 — 25 branches of the first and subsequent orders. Height of a stalk is 60 — 190 cm, thickness of 0,8 — 3,5 cm. Coloring of a stalk green, dark green, glaucous-green, it is covered with a wax raid.
Leaves are next, petiolar, in the lower part of a stalk lirovidno-peristonadrezanny with an oval or roundish stupid top share, sometimes gently rolling, form the compact radical socket; average leaves — elongated and spear-shaped; top — elongated lantsetnye, sedentary, smooth-edged with the expanded basis, on 1⁄3 — 2⁄3. Therefore it is easy to distinguish colza from other representatives of the sort Cabbage. Leaves blue-green or violet, hairless or slightly hairy with a wax raid. Silnooblistvenny and slabooblistvenny forms differ.
Flowers are collected in clustery (shchitkovidny) friable inflorescences. A flower with four yellow petals and elliptic and ovoid chashelistika, a pedicel, six stamens (from which two external is shorter than internal) and one pestle with a golovchaty rylets. At the basis of short stamens two nektarnik are located. The ovary is top, dvugnyozdny, with 20 — 40 semyapochka.
Fruit — the narrow direct or slightly bent pod located under a right or obtuse angle in relation to a stalk, 6 — 12 cm long, 0,4 — 0,6 cm wide. Pod shutters smooth or slabobugorchaty. On length of a pod there passes the filmy partition which is coming to an end in a seedless nose. In a pod of 25 — 30 seeds of rounded spherical shape, slightly cellular, grayish-black, black and gray or dark brown coloring. Seeds are very small, diameter of a seed is 0,9 — 2,2 mm, weight colza of summer and 4 — 7 g has 1000 seeds of 2,5 — 5 g at winter. Seeds keep viability of 5 — 6 years.