Burrs are a common annoyance for homeowners, typically appearing as sharp, spiny seed heads produced by certain weeds that can stick to clothing, pet fur, and bare feet. These prickly structures are part of a survival strategy, designed to cling to passing animals and people for seed dispersal. Controlling them requires a comprehensive approach that moves beyond simple removal to include proper identification, cultural practices, and targeted treatments.
Identifying the Specific Burr Weed
Effective control begins with accurately identifying the specific weed species, as different plants have distinct lifecycles and treatment timing. Burr-producing weeds generally fall into two categories: summer annuals and winter annuals. The most common summer annuals are sandbur, which is a grassy weed, and puncture vine, which is a broadleaf weed.
Sandbur, also called grassbur, is a summer annual grass that thrives in sandy, nutrient-poor soil and starts germinating when soil temperatures reach about 52°F. It produces its painful, spiny burrs in late summer through fall. Puncture vine, also known as goathead, is a broadleaf summer annual that grows low to the ground in spreading mats and produces woody, tack-like burrs that can flatten bicycle tires.
Another common type is lawn burweed, a broadleaf winter annual that germinates in the fall as temperatures cool. This weed grows inconspicuously throughout the winter, but in early spring, as temperatures rise, it quickly develops spine-tipped burrs. For this winter annual, the burrs are already formed by the time they become noticeable in the spring, making prevention the only way to avoid the sharp spines.
Immediate Physical Removal and Cleanup
Once the sharp seed heads have formed and scattered, the immediate priority is removing the existing burrs to prevent them from being pressed into the soil, where they can germinate later. Hand-pulling is effective for small, isolated patches, but care must be taken to ensure the burrs do not dislodge and spread further. Always wear thick gloves and ensure the entire plant is removed before it can drop its seeds.
For larger areas, a highly effective mechanical technique involves dragging an old blanket, rug, or piece of burlap over the infested area. The sharp spines readily catch and adhere to the woven material. This process should be repeated several times to maximize collection.
Specialized yard vacuums can also suck up loose burrs from the lawn surface. After collection, it is crucial to dispose of the collected burrs and plant material safely. The material should be rolled up tightly and double-bagged in heavy-duty plastic trash bags before being placed in the garbage to prevent the seeds from escaping and re-infesting the yard.
Cultural Practices for Long-Term Control
The most durable way to manage burr weeds is to create a dense, healthy lawn environment. Burr weeds are opportunistic, thriving in thin, stressed, or bare patches of turf. Starting with a soil test provides a baseline, revealing any nutrient deficiencies or pH imbalances that weaken the grass and allow weeds to take hold.
Adjusting your mowing height is one of the most effective cultural practices for weed suppression. Mowing at the highest recommended setting for your turf type, often three to four inches, allows the grass blades to shade the soil surface. This shading blocks the sunlight needed for many weed seeds, including sandbur and puncture vine, to germinate. It also promotes deeper root development in your turf, making it more resilient.
Proper watering techniques are also instrumental in long-term control. Shallow, frequent watering encourages grass roots to stay near the surface, making them vulnerable to heat and drought stress. Instead, adopt a deep and infrequent watering schedule that delivers one to one and a half inches of water per week over only two to three sessions. This technique encourages the turf’s roots to grow six to eight inches deep, enabling the grass to outcompete the shallower root systems of most weeds.
Aeration and overseeding should be performed annually, preferably in the late summer or early fall, to combat soil compaction and increase turf density. Aeration creates small holes that relieve compaction, allowing air, water, and nutrients to penetrate the root zone. Overseeding then fills in any thin or bare patches with new, desirable grass, effectively crowding out the space where burr weeds would otherwise establish.
Targeted Herbicide Application
When cultural methods alone are insufficient, a targeted herbicide program can be employed, with timing based on the weed’s lifecycle. For summer annuals like sandbur and puncture vine, the most effective chemical control is a pre-emergent herbicide application in the spring. This application must occur before the weed seeds germinate, typically when the soil temperature consistently reaches 52°F to 55°F. Pre-emergent herbicides create a chemical barrier that stops the seeds from successfully sprouting.
If you miss the pre-emergent window or need to treat existing plants, a post-emergent herbicide is necessary. For the grassy sandbur, selective post-emergent products containing active ingredients like quinclorac or MSMA (where labeled for turf) are effective when the plants are young. For broadleaf weeds like puncture vine and lawn burweed, a combination broadleaf herbicide containing 2,4-D, dicamba, and mecoprop (MCPP) works best.
For winter annuals like lawn burweed, the post-emergent application window is in the late fall or winter, typically December through February, before the burrs form in the spring. Applying a broadleaf herbicide during this cooler period kills the small plant before it has a chance to develop its sharp seed heads. Always read the product label carefully to ensure the herbicide is safe for your specific grass type and follow all application instructions.