Bristly starbur is an invasive annual herb that grows to between 8 and 25 inches tall. It is known for its ability to propogate by means of the star-shaped, hooked spines that are produced on the seed shell, which easily attach themselves to animal fur and clothing.
Seedlings of the bristly starbur tend to emerge between temperatures of 70 and 90 degrees F (20-30 degrees C) and continue to do so until temperatures do not allow. They mature rapidly (45-50 days) and propogate well, often growing in dense patches.
Stems, branches, and leaves are covered in stiff, bushy hairs. The leaves are oval-shaped and arranged opposite. The edges of these leaves are irregularly serrated. Underground, it forms a branched taproot.
The fruit of the bristly starbur is developed in the axils of the upper leaves and begin as pale yellow-green inflorescences 1/4 inches in diameter. As the inflorescence matures, it is arranged into star-shaped clusters of 5-10 wedge-shaped burs with hooked spines covering it. There are two longer spines at the apex of each bur.
Bristly starbur is known to reduce yields as it competes for water and nutrients. It also has the potential to damage or clog harvesting machines. In the presence of animals, it is a toxic plant (though rarely consumed) and reduces the value of wool, as the burs can become stuck throughout. It is considered to be a high risk weed by the USDA due to its strong competition for resources, high potential economic impact, and the plant diseases it can play host to. The crops affected by this weed include peanuts, beans, pineapple, sugarcane, sunflowers, vegetables, cotton, orchards, pastures, rice, soybeans, barley, and wheat.
Bristly starbur is very intolerant to shade and can be easily controlled through planting a heavy cover crop species. Other control methods are using deep-plowing techniques to bury the seeds.
Chemicals including 2,4-D can be used in preemergence to control bristly sanbur seedling emergence. There are also many other herbicides that can control this weed. Please contact your local weed specialist to learn what is most effective in your area and how to use it best. Always read and follow all label instructions.