Brassica tournefortii (BRASSICACEAE) Wild Turnip, Sahara Mustard

Weeds to Whack

An annual herb to 90 cm with light yellow coloured flowers. The flowers have four petals followed by seed pods to 6 cm. The green, mainly basal leaves are pinnately lobed. In South Australia this weed evolved resistance to Group B/2 herbicides in 1996 and infests cereals. A robust, fast-growing, drought-tolerant winter annual that prefers sandy soils. The basal rosette of divided hairy leaves can span three feet in wet years. The nearly leafless flowering stems branch profusely, creating the appearance of a shrub from a distance. The small light-yellow flowers are self-pollinating, large plants produce up to 16,000 seeds. Dried plants break off at the base and tumble in the wind, spreading seeds rapidly. Wet seeds are sticky with mucilage and can be transported long distances by animals and people. This weed grows very fast, smothering native herbaceous plants and competing with shrubs for light and soil moisture. In the winter-spring of 2005 about three-quarters of the most famous wildflower areas in California and Arizona were overrun with Sahara Mustard. Also know as African Mustard. Not common in the catchment.

Photo: Robert Whyte