Sandburs, often called burr grass or sticker weeds, are highly invasive annual grasses that pose a significant nuisance in lawns across the United States. These weeds are notorious for producing sharp, spiky seed heads that easily stick to clothing, pet fur, and bare feet. Effectively managing sandburs requires a multi-pronged approach that targets the plant at different stages of its life cycle. Understanding the nature of this weed is the first step toward reclaiming your turf.
Identifying Sandburs and Their Growth Cycle
Sandburs resemble common crabgrass in their early stages, growing low to the ground with flat, light-green leaves that spread radially from a central point. As they mature through the summer, they develop their distinctive sandbur seed head. This weed is classified as a warm-season annual, meaning it germinates when soil temperatures rise and completes its life cycle within a single growing season.
Germination typically begins in the late spring or early summer, following consistent soil temperatures around 60°F. The plant focuses on vegetative growth until mid to late summer when it begins producing burs. These burs contain the seeds that drop into the soil in the fall, ensuring a new crop of weeds the following year.
Pre-Emergent Chemical Control
The most effective chemical control strategy for sandburs involves using pre-emergent herbicides, which target the seeds before they sprout. These products work by forming a chemical barrier near the soil surface, inhibiting the cell division necessary for the seedling’s root growth upon germination. Correct timing is essential for this method to succeed.
Homeowners should apply the pre-emergent product in the late winter or very early spring, specifically when the soil temperature consistently reaches 52°F to 55°F at a four-inch depth. Active ingredients effective against annual grasses like sandburs include prodiamine, dithiopyr, and pendimethalin. Applying the product too late, once the seeds have begun to sprout, renders this preventative treatment ineffective.
Since sandbur seeds can germinate over an extended period, many regions require a second application for season-long control. This follow-up treatment is generally recommended six to eight weeks after the initial spring application, especially in warmer climates. This strategy maintains the barrier layer, preventing later-germinating seeds from establishing themselves in the turf.
Post-Emergent Removal Strategies
When sandburs have already emerged, the approach shifts from prevention to post-emergent removal. For small, isolated patches, manual removal is an option, although it becomes increasingly difficult and hazardous once the plant begins forming burs. Always use thick gloves and carefully pull the plant, ensuring the entire root system is extracted to prevent regrowth.
Proper disposal is important; removed plants, especially those bearing burs, must be sealed in a plastic bag and disposed of rather than composted. For widespread infestations, chemical control using post-emergent herbicides is the more practical solution. These herbicides are most effective when applied to young plants that have not yet developed mature seed heads.
When treating turfgrass, homeowners must select a selective herbicide, which is designed to kill the weed without harming the surrounding lawn. Products containing active ingredients like MSMA or specific formulations of 2,4-D are often used to target grass-like weeds such as sandburs. Multiple applications may be necessary to eliminate established, larger plants before they drop their seed load.
Non-selective herbicides, such as those containing glyphosate, will kill any plant they contact and should only be used in non-turf areas like cracks in sidewalks, driveways, or garden beds. Efficacy decreases once the burrs have matured and hardened, as the plant is completing its life cycle and is less able to absorb the chemical. Prioritizing removal before seed drop is the ultimate goal of any post-emergent strategy.
Cultural Practices for Long-Term Prevention
Chemical methods offer immediate relief, but long-term sandbur prevention relies on modifying the environment to favor healthy turf over the weed. Sandburs thrive in thin, stressed lawns with dry, sandy, or disturbed soil. The objective is to create a dense canopy that shades the soil, inhibiting the light required for sandbur seed germination.
Raising the mowing height, typically to three inches or higher, allows the turf blades to block sunlight from reaching the soil surface. Furthermore, proper watering techniques encourage deeper, stronger grass roots that can outcompete the shallow-rooted sandbur. This involves deep, infrequent watering sessions rather than light, daily sprinkling.
Improving the overall soil structure is another long-term preventative measure, especially in areas with poor drainage or high sand content. Incorporating organic matter, such as compost, and performing regular aeration helps the soil retain moisture and nutrients, encouraging dense, healthy turf that naturally resists weed invasion. These cultural practices reduce the reliance on repeated chemical treatments.