Burrs are the sharp, spine-tipped seed pods of certain weeds that make a yard uncomfortable for people and pets. These painful structures are designed to cling to fur and clothing for dispersal and are produced by weeds that thrive in compromised turf. Eliminating these nuisances requires identifying the plant, immediate removal methods, and strategic chemical control. This guide outlines methods for eradicating burr-producing weeds and restoring the comfort of your lawn.
Identifying Common Burr-Producing Weeds
Effective control begins with accurately identifying the specific weed responsible for the burrs, as treatment timing depends on its life cycle. Two common culprits are Lawn Burweed (Soliva sessilis), also known as stickerweed, and Sandbur (Cenchrus species). Lawn Burweed is a winter annual that germinates in the fall as temperatures cool, remaining small throughout the winter months.
Lawn Burweed has small, low-growing, fern-like leaves that are finely divided, often forming a dense mat. As spring temperatures rise, the plant forms spine-tipped burrs in the leaf axils; these painful structures persist long after the plant dies. Sandbur, conversely, is a summer annual grass that germinates in late spring and grows through the summer and fall.
Sandbur produces spiny burrs on a spike-like seedhead that detach easily. Understanding the life cycle difference is crucial: Lawn Burweed burrs appear in spring from plants that started in fall, while Sandbur burrs appear later in the summer from plants that started in spring. The best time to treat the plant is always before the burrs harden and drop.
Physical and Manual Removal Techniques
For small infestations, physically removing the weeds offers an immediate, non-chemical solution that prevents seed production. Manual pulling is most effective when the plants are young and the soil is moist, ensuring the entire root system is extracted. It is important to pull these weeds before the burrs have matured and hardened, especially for Lawn Burweed in late winter or early spring.
Once burrs have formed and fallen, the focus shifts to collecting the prickly debris from the soil surface. A simple, low-cost method is to drag an old blanket, towel, or piece of burlap across the affected area. The sticky burrs will readily cling to the coarse fabric, which can then be disposed of in a sealed bag to prevent seed dispersal.
For larger areas, a shop vacuum with a hose attachment can suction the burrs out of the turf, although this is labor-intensive. Specialized lawn sweepers or dethatching rakes may also collect surface debris. However, their effectiveness depends on the density of the turf and the depth of the burrs. Removing the physical burrs, even after the plant is dead, is necessary to immediately restore the comfort of the lawn.
Targeted Herbicide Application
Chemical control is often the most effective method for widespread burr weed infestations, requiring strategic application based on the weed’s life cycle. Herbicides are classified into two types: pre-emergent and post-emergent. Pre-emergent herbicides (containing prodiamine, dithiopyr, or isoxaben) are preventative treatments that create a chemical barrier in the soil to stop seeds from germinating.
For Lawn Burweed, which germinates in the fall, apply pre-emergent herbicide in late September to early October, before soil temperatures drop below 70 degrees Fahrenheit. Sandbur, a summer annual, requires pre-emergent treatment in the early spring before its seeds sprout. Following label instructions for repeat applications, often eight weeks later, increases the efficacy of the chemical barrier.
Post-emergent herbicides kill actively growing weeds. For broadleaf weeds like Lawn Burweed, a three-way herbicide containing 2,4-D, dicamba, and mecoprop (MCPP) is typically effective. The optimal timing for application is during the cooler winter months (December through February) when the plant is small and has not yet developed its spiny fruit.
Applying post-emergent herbicides must occur before the burrs harden in the spring; killing the plant afterward still leaves the painful, mature burrs behind. When treating warm-season grasses like St. Augustine or centipedegrass, use herbicides containing atrazine or reduced rates of the three-way combination to prevent turf injury. Always read the product label for specific temperature restrictions, avoiding applications when temperatures exceed 90 degrees Fahrenheit, and ensure the herbicide dries on the leaf surface before irrigation or rainfall.
Long-Term Lawn Health and Prevention
The ultimate defense against burr weeds is establishing a dense, healthy lawn that naturally crowds out invasive species. Burr weeds thrive in thin, weak, or patchy turf where sunlight easily reaches the soil, allowing seeds to germinate. Adjusting cultural practices to favor the grass makes the environment less hospitable for weeds.
Adjusting the mowing height is important; keeping the grass slightly taller (3 to 4 inches) shades the soil and physically inhibits weed germination. Deep and infrequent watering, rather than light daily sprinkling, encourages a deeper, stronger root system for the turfgrass, helping it outcompete weeds for resources.
Addressing soil health through regular testing is beneficial, as burr weeds often colonize areas with poor or compacted soil. Aerating the lawn annually reduces compaction, allowing for better water and nutrient absorption, which promotes healthier turf growth. Balanced fertilization based on soil test results ensures the turf has the necessary nutrients to maintain vigor and density, suppressing future burr weed infestations.