Sand burrs, or sandspurs (Cenchrus species), are a painful nuisance, especially for those who enjoy their lawn or garden barefoot. These warm-season annual grasses produce hardened, spiny seed heads that easily cling to clothing, pet fur, and skin. Sand burrs thrive in thin turf and sandy, low-fertility soils, often taking over areas where desirable grass struggles. Eliminating an infestation and preventing its return requires a precise, multi-year strategy targeting the weed across its entire life cycle. This approach combines physical removal, timely chemical treatments, and long-term improvements to soil and turf health.
Understanding the Sand Burr Life Cycle
The sand burr is a summer annual weed in most regions, meaning it germinates from seed each spring and dies with the first hard frost of autumn. Seed germination begins when soil temperatures consistently reach approximately 52 degrees Fahrenheit and peaks as soil temperatures approach 75 degrees Fahrenheit. This temperature-dependent timing, usually occurring in late spring or early summer, dictates when control methods must be applied for maximum effectiveness.
The defining feature of this plant is the bur itself, a specialized floret protecting one to three seeds inside. This structure allows seeds to remain viable in the soil for several years, creating a persistent seed bank. The plant roots at its lower nodes, forming a dense mat that easily outcompetes weakened turfgrass. Targeting the plant before it produces these spiny seeds is the foundation of any successful eradication plan.
Manual and Cultural Removal Techniques
For small or isolated patches, physical removal is an immediate and effective non-chemical solution. When hand-pulling, wear thick gloves to avoid injury from mature burs and ensure the entire root structure is removed. Pull plants while they are young, before they develop hardened seed heads, to prevent accidentally scattering seeds.
In areas with a widespread, dense infestation, cultural practices can significantly reduce the seed population. Mowing the area low to the ground and collecting the clippings in a bag helps to gather existing burs before they drop and spread. After a low mow, raising the cutting height for subsequent cuts encourages the desirable turf to grow taller, shading the soil and making it less hospitable for sand burr germination.
For clearing a heavily infested, unplanted area, solarization uses intense heat to kill weeds and seeds. This involves covering the area with a clear or black plastic tarp, watering the soil underneath, and leaving it sealed for several weeks during the hottest part of summer. The trapped solar energy raises the soil temperature high enough to destroy existing plants and many dormant seeds in the top layer of soil.
Effective Chemical Control Strategies
Pre-Emergent Control
The most effective chemical strategy for sand burr management is using pre-emergent herbicides, which establish a chemical barrier in the soil to stop seeds from sprouting. Application timing is paramount; the herbicide must be in place before the soil temperature reaches 52 degrees Fahrenheit. This usually means applying the product in late winter or early spring, often coinciding with crabgrass control timing.
Active ingredients like prodiamine or pendimethalin are reliable for creating this protective barrier. After application, the pre-emergent herbicide must be activated by moisture; water the area with at least a half-inch of irrigation or apply just before rainfall. Because the sand burr growing season is long, a second application eight to ten weeks after the first maintains the barrier throughout the summer.
Post-Emergent Control
When sand burrs have already germinated and are actively growing, a post-emergent herbicide is necessary to kill existing plants. These products are most successful when applied to young, seedling sand burrs that have not yet formed spiny seed heads. Once the burs harden, the plant becomes more resistant to chemical treatments.
For selective control in turfgrass, herbicides containing quinclorac are a common choice for targeting young grassy weeds. Combination products including quinclorac along with broadleaf weed killers such as 2,4-D and dicamba are also successful. Confirm that the selected product is safe for the specific type of grass in the lawn, as some combinations can harm varieties like St. Augustine or Centipede grass. Always follow the product label directions precisely, especially regarding application rates and the need to add a non-ionic surfactant, which helps the chemical adhere to the waxy leaf surface.
Preventing Future Sand Burr Infestations
Long-term sand burr prevention relies on improving the overall health and density of the turfgrass, making the environment unfavorable for the weed. Sand burrs are opportunistic weeds that flourish in bare spots and thin turf, especially where the soil is sandy and lacks nutrients. A thick, robust lawn naturally crowds out sand burr seedlings by competing for sunlight, water, and nutrients.
Implementing a consistent fertilization program, based on soil testing, corrects nutrient deficiencies that weaken turf. Proper watering practices also play a role in prevention; a deep, infrequent watering schedule encourages deep grass roots while discouraging the shallow-rooted sand burr. Mowing at the highest recommended height for the specific turf type creates a dense canopy that shades the soil, keeping the ground cooler and inhibiting sand burr seed germination.