Description
Flower and Wild Growth of African Mustard.
Brassica tournefortii is described as an annual herb with stems 10 to 100cm tall. The plants flower early; the small, dull yellow flowers are inconspicuous compared to most other true mustards. Petals are less than 5 to 7mm. Individual flower stalks are longer than the sepals and spread away from the stem. Fruits have an obvious beak at the tip. The pedicels of the fruits are 4 to 10mm long and diverge stiffly from the stem at a forty-five degree angle. B. tournefortii shows variability in size depending on the availability of soil moisture. Drought-stressed plants can reproduce with leaves as small as 8cm long and on sandy soils with sufficient moisture leaves have known to grow to more than 50cm long, giving the plant a 1m spread, making it the largest herbaceous rosette plant in the region.
Occurs in:
desert, range/grasslands, ruderal/disturbed
Habitat description:
Brassica tournefortii is especially common in areas with wind-blown sediments. This species is also invading exotic annual grassland and coastal sage scrub. It often forms almost pure stands on abandoned sandy fields. B. tournefortii is most common in disturbed sites such as roadsides and abandoned fields, and that it can be found, but is scarce, on alluvial fans and rocky hill slopes.B. tournefortii is especially common in sandy lowland habitats across the Sonoran Desert, including low dunes, interdune troughs, sandy flats, and sandy-gravelly washes.”
General impacts
Dense stands of B. tournefortii appear to suppress native wildflowers. Because of its early phenology, it appears to monopolise available soil moisture as it builds canopy and matures seed long before many native species have begun to flower. This species also locally dominates exotic grasslands in dry, open sites, especially disturbed areas. It expands over larger areas when drought suppresses other exotic annuals such as Bromus rubens, Avena fatua, Brassica geniculata, and Erodium cicutarium. B. tournefortii increases fuel loads and fire hazard in desert scrub and coastal sage scrub. It also establishes from a soil seed bank after fire. B. tournefortii is especially common in sandy lowland habitats across the Sonoran Desert, including low dunes, interdune troughs, sandy flats, and sandy-gravelly washes.
Native range:
Out of Control Bush of African Mustard.
Africa, Asia, and Europe (USDA-GRIN, 2003)
Known introduced range:
Australia, and North America (Adkins et al. 1997, and USDA-NRCS 200)
History:
Brassica tournefortii probably was introduced with date palms brought from the Middle East in the early part of this century with the development of the date industry in the Coachella Valley.
Management information:
Mechanical:
The spread of B. tournefortii can be reduced by controlling it along roadsHand pulling of B. tournefortii might be effective in limited areas when seed pools have been suppressed. Planned burns may not be a useful option. Since B. tournefortii establishes from a seed bank, it is doubtful that grazing could suppress the spread of this annual. The establishment of dense cover of exotic annual grasses apparently suppresses this species.”
Chemical:
Close up of African Mustard Flower.
In selected areas herbicide treatment may be effective.so early treatment may reduce its abundance and allow later-germinating natives to establish.
Biological:
Invaders of the Sonoran desert state that “It is unlikely that a biological agent, if found, would be approved because many important crop plants are in the genus Brassica (e.g., cabbage, cauliflower, broccoli, brussels sprouts). There are also numerous native mustards that might be threatened by a biological agent”.
Principal sources: Sanders and Minnich, 2000 Brassica tournefortii
