The sandbur (Cenchrus longispinus), or long-spine sandbur, is a rather unusual grass. Its flat stems are sometimes upright, but frequently they are bent near the base. This allows the plant to grow low to the ground, sometimes forming large mats.
The plant as a whole has a coarse appearance. The tapered leaves are rough to the touch, and their sheaths frequently have hairy margins. More impressive, however, is the inflorescence. This is a spike 1 to 3 inches long that develops into a hard, hairy mass of up to 20 burs, each covered with spines.
The sandbur is common through the United States, where it is mostly considered a noxious weed. It may occur in any part of Kansas.
As its name suggests, the sandbur prefers sandy or gravelly soils, preferably somewhat on the dry side and in full sunlight. It thrives in waste areas of all kinds, including neglected fields, lawns, and roadsides.
The sandbur is an annual. Its seeds start to germinate in late spring and continue to show signs of life throughout the summer. At first, it looks innocuous enough, especially as its stems tend to be more upright early in the year. However, as early as July, it begins to flower and form its hallmark burs.
These burs contain the seeds. The burs serve as an effective transportation mechanism, hooking themselves onto anything that walks by and traveling to new locations. Once deposited in the soil, the seeds may remain viable for up to five years.
Sandbur plants continue to grow until the first hard frost.
Despite its ill repute, the sandbur is a native species, and it does serve a purpose. It is an aggressive colonizer species, whose job is to reclaim bare ground and protect it from erosion and further damage.
When young and more obviously grassy, the sandbur actually does have some forage value. However, as soon as the burs appear, the plant quickly loses its usefulness to livestock producers.
Sandbur is considered a nuisance weed to livestock producers because the spiny burs can injure livestock.
But it is in the yard that the sandbar is most annoying. For starters, it clings to clothing and injures pets. Furthermore, it can quickly invade a thin, poor lawn in dry years. Dealing with sandburs in the lawn requires persistence and attention to building the health of the more desirable grasses. Adjust the pH if necessary, water deeply if rains are slow in coming, mow high to allow grass roots to take hold, and reseed sparse patches.
If sandburs have already moved into your yard, mow frequently to prevent the plants from growing seed. Rake up any debris after mowing. You can also dig up sandbur plants with a garden knife—just be sure to wear thick leather gloves when handing them!
Barnyard grass is unattractive enough to give you a brief scare at first sighting, but it is not a threat. Look closely at the inflorescence—instead of a spike full of burs (rounded objects covered in sharp spines), it grows a branching panicle covered in harmless bristles.
Parts of a Grass Plant: A Glossary
Definitions for technical terms used in this post.