This winter and spring's wet, mild conditions have been perfect for many wild plants. Although it has been a great year for wildflowers, several non-native plants have also been blooming and threatening our native wildflowers.
One invasive plant has been especially common along roadways from Central Texas to Port Aransas to DFW. Known as bastard cabbage (Rapistrum rugosum) it forms large masses several feet tall of small, highlighter yellow flowers. Another invasive, or harmful, plant that will likely be seen in growing numbers this summer is Malta star-thistle (Centaurea melitensis). It has small prickly flowers and blue-grey foliage.
The great weather has allowed these unwanted species to flower profusely and to produce lots of seed to potentially be a much larger problem next year. Because they compete for space and for resources with native plants, they could reduce next season's wildflower displays. So what can you do about invasive plants such as these?
Addressing These Invasives
First, mowing will remove some, but not all, flowers and reduce the amount of seed that could grow into a new invasive plant next year. But mowing doesn't remove all the seed stored in the ground. A better strategy is to remove the whole plant, root and all, or to kill an invasive plant with herbicide before the flower heads go to seed. (Since herbicides can also kill wildflowers you want and have other potential drawbacks, use them carefully and sparingly).
Timing your eradication efforts appropriately can help. Invasive plants are best attacked in the fall and winter after they have started to grow (germinated), but while they are still small, ground-hugging rosettes. They can be physically or chemically treated to kill them, and the area they were in resown with seeds from native species. Research conducted by the Wildflower Center has shown that sowing large amounts of seed of our own native wildflowers can reduce the population of an invasive such as bastard cabbage by competing with it for resources.
It is best to mark the initial locations of invasive plants that are treated in the spring or summer so that they can be revisited and treated again in the fall. Being able to identify what a young seedling of a particular invasive plant looks like is essential so eradication efforts specifically target them. To learn what bastard cabbage, malta start thistle and other plants that are invasive in Texas look like as young and adult plants, visit www.texasinvasives.org.
By Mark Simmons