If you drive the country side this time of year you have probably noticed the abundance of plants with small yellow flowers on the roadside and in some pastures. These are a combination of “Common Broomweed” and “Bitter Sneezeweed,” which bloom August through October.
Broomweed is a native warm-season broad leaf plant of the sunflower family. It usually produces one erect stem (the broom “handle”) arising from a deep tap root. It also makes a bushy head (the “broom”) which produces small yellow flowers with tiny brown seeds. These seeds can be an important food source for quail and other wild birds.
Common broomweed is very prolific and can grow into thick stands that completely shade the ground and out-compete grasses for soil moisture and nutrients. This canopy can obstruct livestock access to grasses and cause eye irritations for many years. As the top canopy dies it is very resistant to breakdown and remains as a brittle barrier over desirable forages that livestock are hesitant to penetrate, which causes spot grazing in areas that have less broomweed coverage.
Bitter sneezeweed also a warm season broad leaf has a deep and very strong tap root. Its name is derived from its bitter taste and pungent odor. Unlike broomweed, bitter sneezeweed is a known toxic plant producing a sesquiterpene lactone which is at highest levels in the plant at flowering time, but due to the bitter taste and odor it is seldom consumed at levels to be lethal to grazing livestock. The toxin is stable in the plants even after cutting, therefore contaminating harvested forages for hay.
Drought, shortage of hay and lack of standing forages this year leads to over-grazed pastures which sets up the perfect environmental conditions for a bumper crop of both common broomweed and bitter sneezeweed. Seasonal rainfall patterns also greatly influence the germination and growth of these weeds. Adequate winter soil moisture for seedling emergence and spring rains extend plant survival through the seed producing stage.
Both of these weeds can be controlled in late spring with the application of a 2,4-D herbicide, but may require more than one application during a prolific growing year. Mowing at the bloom stage will only spread the thousands of tiny seeds and possibly increase plant population while reducing the competitive ability of perennial forages. Once the seed base is built up, periodic infestations will continue despite any control methods used.
So enjoy the fall yellow blooms and the history to which it came.
Educational programs conducted by the Texas AgriLife Extension serve people of all ages regardless of socioeconomic level, race, color, sex, religion, disability or national origin.
Eddie Baggs, Denton County Extension Agent-Agriculture
Texas AgriLife Extension – Denton County
(940) 349-2880 or Metro (972) 434-8812