Description
African Turnip Weed (Sisymbrium thellungii) is an annual herb that grows up to 60 cm tall. The stems and leaves are covered in backward-pointing stiff hairs. The basal leaves (up to 30 cm long) have 3-7 pairs of lobes, the terminal lobe being the largest. The upper leaves are similar in appearance to the basal leaves, but diminish in size along the stems. The flowers consist of four yellow petals. Each petal is up to 8 mm long. The fruits are long and narrow (7-12 cm long, 2-2.5 mm wide) and are usually covered in stiff hairs. The short stalks that attach the fruits to the stem point away from the stem, causing the fruits to be spread widely. The seeds are small (about 1 mm diameter) (Marais 1970; Hewson 1982).
For further information and assistance with identification of African Turnip Weed contact the herbarium in your state or territory.
Distribution:
In Australia, African Turnip Weed is naturalised in south-east Queensland and north-east New South Wales (Hewson 1982). It is not common in New South Wales (Retter & Harden 1990), and has only been recorded from the New England Tableland region. In Queensland, it was first recorded in 1947 as a common weed on fallow land in the Port Curtis district. Herbarium records indicate that the species has been present in the Queensland districts of Warrego, Cook, Darling Downs, North Kennedy, Mitchell, Moreton, Port Curtis, Leichardt, Burnett, Wide Bay and Maronoa (Queensland Herbarium 2007).
Habit:
Herb
Key points:
- African Turnip Weed (Sisymbrium thellungii) is a common weed in the Queensland cropping belt.
- Herbicide resistant populations of African Turnip Weed have been recorded in Queensland.
- African Turnip Weed is considered a weed of agriculture but it has also been recorded as a weed of natural systems.
- African Turnip Weed is able to grow on a wide range of soil types and can invade cropping and pasture land.
How it spreads:
African Turnip Weed is an annual species, hence reproduction occurs by seed. Although no published information could be found on the dispersal mechanisms used by African Turnip Weed, it is assumed that it spreads in a similar manner to other annual weedy cruciferous species such as Wild Radish (Raphanus raphanistrum) and Sand Rocket (Diplotaxis tenuifolia). These species spread by water, especially where plants grow in riparian habitats and on steep terrain where erosion and runoff occurs. Contaminated soil, fodder, vehicles and other equipment are potential vectors for seed transport. Seeds may also be readily dispersed along roadsides during roadside maintenance works. Dispersal via contaminated agricultural produce is also a potential means of spread (Parsons & Cuthbertson 2001).
Where it grows:
In Queensland, African Turnip Weed has been found growing on a wide range of soil types as a weed of roadsides, railway lines, pasture, crops, fallow, alluvial flats, river banks and dry forest (Queensland Herbarium 2007).
Flower colour:
Yellow
Impacts:
In Australia, African Turnip Weed is considered a weed of the natural environment and as a weed of agriculture (Randall 2007). In Queensland, it has been recorded invading pasture, wheat crops, fallow land, dry sclerophyll forest, disturbed areas, railway lines, roadsides, wetlands, riparian open forests and floodplains (Queensland Herbarium 2007). It is considered a common weed in the Queensland cropping belt (Dellow et al. 2006). African Turnip Weed can dominate crops and pastures. Young plants grow vigorously, even under moisture stress, out-competing other more valuable species (Wilson et al. 1995).
In South Africa, where it is considered native, it occurs as a weed in crops (especially cereals), waste areas, orchards and on roadsides (Bromilow 2001).
Seed of African Turnip Weed was found to be harmless to pigs even when fed at high levels (Blaney 2004).
Origin:
African Turnip Weed is native and widespread in the eastern part of South Africa (Marais 1970).
History:
African Turnip Weed was first recorded in Australia in 1947 as a common weed on some fallow land in the Port Curtis district in Queensland (Queensland Herbarium 2007). It is not known how or why African Turnip Weed arrived in Australia.
