BRASSICACEAE - Cabbage Family

Formerly known as the Cruciferae, because it has four petals held open in the shape of a cross, this family includes many important vegetables and agricultural crops. There are over 3000 species throughout the world, but the largest number are from temperate regions of the Northern Hemisphere. In Western Australia there are 54 native species and about 40 naturalised. Several have bright yellow flowers and can be difficult to distinguish from each other before fruits have formed. As a result, some species may be overlooked when in flower, by assuming that they are more familiar species. Identification therefore often relies on the presence of mature fruits. The fruits may have a "beak" at the end and are often divided internally by a longitudinal septum. For identification purposes, the family is usually divided into those species with fruits more than three times as long as broad (excluding the 'beak'), in which case the fruit is termed a siliqua, and those in which they are less than three times as long as broad, in which case the fruit is referred to as a silicula.
Alyssum linifolium (flax-leaf alyssum) is an annual herb, up to about 30cm. The leaves are narrow, grey, and densely covered in short hairs. The fruit pod is a silicula up to 6mm long, flattened parallel to the septum, containing four to six seeds on each side. It flowers in spring and the white petals are 2-3mm long. It is a scattered weed of woodlands in the Goldfields and is native to southern Europe, western Asia and possibly also to Australia.

Eight species of the genus Brassica have been recorded as weeds in Western Australia. Although pictures of only one is shown here, it is important to distinguish between them; some species may be under-recorded because of incorrect identification.
B. barrelieri subsp. oxyrrhina (was B. oxyrrhina) (smooth-stem turnip) is an annual to 50cm. Its leaves are pinnately divided with the sharp lobes pointing towards the leaf base and stiff hairs on the undersurface of the midrib. The stem of the inflorescence is only slightly hairy at the base or not at all. The petals are 6-8mm, white or pale yellow with distinct purple veins. The fruit is a siliqua, 2.5 to 6cm long with a beak (containing one or two seeds) 1-3mm long. It flowers in spring and is recorded occasionally from the wheatbelt, disturbed coastal sites and road verges in Perth. Probably more common than currently recorded. Native to the Iberian Peninsula.
B. fruticulosa (twiggy turnip) is an annual or short-lived perennial, up to 50cm tall. It is one of the least leafy of the introduced Brassica species. The petals are pale yellow, about 10mm long. The flowers are produced in spring and summer. The narrow siliquas are 2-4cm long and constricted around the seeds, giving them a knobbly appearance. It is a weed of urban waste ground and railway lines. It has been recorded from a few locations in Perth and probably has the potential to spread in urban and horticultural areas. Native to the Mediterranean. Possibly introduced as a vegetable.
B. juncea (Indian mustard) is an annual, up to 1m tall. The leaves are blue-green. The petals are 7-9mm long, pale yellow and the fruit 2-6cm long, with a beak more than 4mm. It can be distinguished from B. rapa, B. oleracea and B. napus by its stalked upper stem leaves. This species is occasionally grown as a crop in Western Australia, probably the source of its introduction. However, although widespread in agricultural areas, it is not common. Native of Europe and Asia. Flowers in spring.
B. napus (oilseed rape, rapeseed, canola) is now becoming a widespread crop, and this annual species is found commonly along roadsides in the south-west of the State, where it may have spilt from trucks. However, these populations often seem to persist under these disturbed conditions. Leaves are blue-green (unlike B. rapa), those at the base may be bristly. The petals are 11-14mm, bright yellow. The fruits are 4.5 to 10cm long. Its stems may reach 1.5m, but along road verges it is usually much shorter. Flowers in spring. May have originated as a hybrid of B. oleracea and B. rapa.

B. nigra (black mustard) is an annual, to 1m. The flowers are bright yellow, with petals 7-9mm long. The fruit pods are 1-2cm long, the beak less than 4mm. The lower leaves are bristly. The only naturalised species of Brassica with its fruits, that are distinctly four-sided, held closely along the main stem on maturity. Occasionally recorded as a weed of cropping in the south-west of Western Australia. Formerly grown as a crop. A native of Europe.

B. oleracea includes cabbage, broccoli and cauliflower among its various cultivated forms. In the weedy form, the leaves are blue-green (in contrast to B. rapa) and completely hairless. It is an annual, to 1m. The petals are 10-20mm long, usually longer than B. napus. It flowers in spring. Its fruits can be among the longest of the Brassica species in Western Australia, up to 10cm. It is an occasional weed in the south-west of the State. Native of Europe. B. rapa (turnip) is an annual to 1m, and is the weedy form of the vegetable turnip. Along with B. napus and B. oleracea, the upper leaves clasp around the stem. Unlike those species, its leaves are a bright green and its petals are the brightest yellow and the lower leaves may be bristly. The fruit is a siliqua, 4-6.5cm long. It has probably escaped from cultivation, but where it occurs as a weed, its root does not swell as in the vegetable form. It is infrequently reported as an agricultural weed; in some areas, such as Albany, it can be the dominant weed in market gardens.
B. tournefortii (wild turnip) is an annual to 60cm. The leaves are pinnate, with sharp lobes pointing backwards towards the leaf base and densely covered with bristles, particularly on the underside. The inflorescence is densely hairy, although hairs become sparser towards the top. the petals are pale yellow or cream to white, 5-8mm long. The fruit is a siliqua, 3-7cm long with a beak 1-2cm long. It is a common weed of wasteland, roadsides, grazed woodlands, shrublands and islands; a widespread weed of horticulture and of crops in the agricultural areas. Found from Carnarvon to Eucla.

Brassica tournefortii , RR

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