As one drives along the highways and back roads in the Hill Country, they’ll likely see fields of tall, bright yellow flowers taking over the roadside and surrounding countryside. More than likely this is bastard-cabbage or Rapistrum rugosum.
Bastard cabbage is also known as turnip- weed, common giant mustard, ball mustard, wild turnip, wild rape and tall mustard-weed. This time of year, the weed is often seen taking over roadsides and filling fields with its dainty yellow blooms. The plants may appear lovely blowing in the breeze, but they are a very noxious weed. It is designated as such by both the state and federal government.
Bastard cabbage typically flowers from early spring into summer, bearing clusters of small, showy yellow flowers at the tips of its branches. Annual bastard cabbage seeds germinate early in the growing season (late fall or early winter) and quickly cover the ground with a blanket of leafy rosettes (circles of leaves at ground level that resemble the greens on dandelions) that spread and cover much of the ground around the flower. These dense greens block sunlight from reaching seeds and seedlings of native plants. Bastard cabbage often threatens to choke out Texas’s bluebonnets.
The highly invasive plant should be removed when and wherever possible. Manual removal of the plant and its taproot — as well as the disposal of seeds — is effective, though labor-intensive. It is relatively easy to pull individual plants from established populations of bastard cabbage, so if it is found in a small enough field, get yanking. If the field is bigger, mobilize a pulling party with neighbors. Be sure to pull out the entire plant before it goes to seed.
Mowing will remove some flowers and reduce the amount of seed that could grow into a new plant next year, but it doesn’t remove the seed stored in the ground.
No matter which way bastard cabbage is removed, Lady Bird Johnson Wildflower Center research recommends planting more native seeds in areas that are heavily seeded with one of Texas’s top native wildflowers, the Indian Blanket. Bastard cabbage has a tough time competing for water, light and nutrients with this native and could reduce the bastard cabbage population.
