Sand spurs (sandburs) are annual grassy weeds that thrive in sandy, dry, and thin turf areas, quickly colonizing bare patches where healthy grass struggles to grow. The primary problem is the production of spiny seed heads, or burrs, which are painful to step on and easily cling to clothing, fur, and shoes, leading to rapid spread. Eliminating these invaders requires a selective strategy that targets the weed without damaging the surrounding turfgrass. The solution involves a combination of chemical control at the right time and long-term cultural practices designed to strengthen the lawn against future infestation.
Choosing the Right Herbicide
Selective sand spur control involves a two-pronged chemical attack using pre-emergent and post-emergent herbicides. Pre-emergent herbicides create a chemical barrier in the soil that prevents sand spur seeds from germinating. Timing is paramount, requiring application in early spring when soil temperatures consistently reach 52 to 55 degrees Fahrenheit, generally before the weed sprouts.
Active ingredients like prodiamine and pendimethalin are recommended for selective pre-emergent control. These chemicals stop the growth of the newly sprouted root system, killing the weed seedling before it emerges. However, sand spurs produce a relatively large seed, which can sometimes challenge the efficacy of a single pre-emergent application, making a split application necessary.
Once the sand spur has emerged, a post-emergent herbicide is required to kill the existing vegetation. This treatment is most effective when the plants are young, typically in late spring or early summer, and before the painful burrs have formed. Specific selective herbicides are available for warm-season turf types.
For Bermuda, Zoysia, and Centipede grass, herbicides containing imazaquin are often effective against young sand spurs. Another option for broad-spectrum control is the active ingredient thiencarbazone-methyl, often combined with other herbicides like iodosulfuron-methyl-sodium. It is necessary to check the product label to ensure the chosen herbicide is safe for your specific turf type. For example, some selective chemicals, such as sethoxydim, are only safe for use on centipedegrass and will damage others like bermudagrass.
Non-Chemical Control Techniques
While chemical control offers immediate results, non-chemical techniques can reduce sand spur populations without harming the turf. Hand pulling is practical for smaller infestations, but must be done before the plant produces spiny burrs, which can break off and remain in the soil, ensuring the weed returns. Once the burrs have matured, mechanical removal of the plant can inadvertently spread the seeds further throughout the lawn.
Adjusting mowing habits provides non-chemical defense against the weed. Mowing the lawn at the highest recommended height for your turf species helps the grass blades shade the soil surface. This shading reduces the amount of sunlight reaching the soil, which discourages the germination of sand spur seeds.
Use a grass catcher and bag the clippings when mowing areas where sand spurs are present. This action prevents the mature burrs, which are filled with seeds, from being redistributed across the lawn by the mower blades. Targeted irrigation practices can also favor the turf over the sand spur.
The sand spur is adapted to dry, sandy conditions, so deep and infrequent watering encourages the establishment of deep turfgrass roots. This practice helps the healthy lawn outcompete the shallow-rooted sand spur for moisture and nutrients during periods of drought stress. Limiting surface moisture can also make the environment less conducive for sand spur seedling establishment.
Promoting Turf Resilience and Prevention
The long-term solution to controlling sand spurs is creating a dense, healthy lawn that naturally crowds out the weed. Sand spurs are opportunistic and primarily invade areas where the turf is thin or stressed, often due to poor soil conditions. Therefore, improving soil health is a foundational step in prevention.
A soil test should determine the soil’s pH and nutrient levels, as sand spurs thrive in the low fertility and acidity common in sandy soils. Correcting these deficiencies, particularly with lime to adjust pH or specific nutrient applications, allows the preferred turfgrass to establish a robust root system. Proper fertilization, especially with timely applications of nitrogen, is important for promoting the vigorous growth needed to increase turf density.
A thick, competitive canopy of grass blocks the sunlight that sand spur seeds require to germinate. Applying fertilizer according to the turf species’ specific needs will ensure the grass can physically outcompete the weed for light, water, and available nutrients. This dense growth habit is the most effective natural barrier against weed invasion.
Aeration and dethatching are cultural practices that contribute to turf resilience by addressing soil compaction. Compacted soil restricts oxygen and water movement, which stresses turfgrass roots and creates an environment where sand spurs can easily take hold. Relieving this compaction through core aeration allows grass roots to penetrate deeper and encourages lateral growth, further enhancing the turf’s ability to outcompete the weed.