- Subspecies, varieties and synonyms: Field Mustard, Turnip Mustard, Wild Mustard, Wild Kale, Bird Rape, Navew, Cale, Annual Turnip Rape (ssp. campestris), Turnip (ssp. rapa), Turnip Rape, Winter Turnip Rape
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Annual or biennial herb. Root thin (ssp. campestris, ssp. oleifera) or swollen, wide and flat, yellow–white (ssp. rapa).
- Height: 40–100 cm (16–40 in.). Stem glabrous–sparsely haired.
- Flower: Corolla regular (actinomorphic), yellow, approx. 1 cm (0.4 in.) wide, petals four, 6–10 mm (0.24–0.4 in.) long. Sepals 4. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme, extending in fruiting stage. Open flowers reach higher up than the buds.
- Leaves: Alternate, lowest stalked, stalk winged, hairy, upper leaves stalkless, amplexicaul. Blade glabrous, underside hairy along veins, basal leaves shallowly lobed–with toothed margins, bright green, stem leaves with entire margins, bluish green.
- Fruit: Many-seeded, opening lengthwise, 5–6 cm (2–2.5 in.) long, spreading siliqua, tip usually with 1–1.5 cm (0.4–0.6 in.) long seedless beak. Stalk approx. 15 mm (0.6 in.).
- Habitat: Fields, vegetable gardens, mills, roadsides, loading areas, rubbish tips.
- Flowering time: June–July(–August).
Wild turnip, turnip rape, and turnip all belong to the same, very diverse species Brassica rapa. Of the subspecies, only wild turnip (ssp. campestris ) grows ferally in Finland. Before World War II it was a reasonably common weed in the vegetable garden, but nowadays it is much rarer. Weeds do not usually get much attention, so wild turnip has been able to decline without any fuss and the reasons remain obscure. Nowadays it can be found mainly in remote fields and vegetable gardens. Wild turnip shares its fate with a whole bunch of weeds that thrived in bygone days but now seem to be in irrevocable decline as they disappear from the vegetable patch. Turnip rape (ssp. oleifera) is an oil plant that is larger and stouter than wild turnip and which is more branched. It is probably the first cultivated form of the plant from around 4,000 years ago. Cultivation and further breeding has happened on three different fronts: in India, China, and in Europe north of the olive oil region. Turnip rape has been cultivated for its oily seeds from cool areas to the tropics. Spring turnip rape has taken over from autumn turnip rape nowadays in Finland in the popularity stakes.
Turnip (ssp. rapa) is a biennial root vegetable, and Finns are also familiar with the leaf vegetable version Chinese cabbage (ssp. pekingensis), which has been developed in the Far East. A number of Asian leaf vegetables that are similar to kale and even broccoli have also been developed (e.g. pak-choi, ssp. chinensis). Turnip and turnip rape are quite common left-overs and escapes from cultivation and can be found e.g. beside roads, where the seeds have fallen from a delivery.
Flowering turnip rape can be told apart from its close relatives rapeseed and swede (B. napus) in that the latter two are bluish green throughout and glabrous. Turnip rape’s flowers are also slightly smaller and the inflorescence is rounded in its early and intermediate stages, even having notched tips because the recently-opened flowers reach higher up than the buds.