The term “burr weed” broadly refers to two distinct annual plants that create painful, spiny seed pods: Soliva sessilis (Lawn Burweed or Spurweed) and Tribulus terrestris (Puncturevine or Goathead). Both are aggressive invaders of lawns and disturbed areas, and both require proactive control to prevent the development of their signature spiky seeds. Successful eradication relies entirely on identifying the specific plant and targeting it within its life cycle, before the burs mature and fall to the soil.
Identifying the Target and Vulnerable Timing
Lawn Burweed (Soliva sessilis) is a winter annual; its seeds germinate in the cool soil of fall and early winter. This low-growing plant forms a small, parsley-like rosette that is often inconspicuous until late winter or early spring. The most vulnerable time for treatment is during this cool period when the plants are small and actively growing, before the burrs begin to form (around March to May). Killing the plant after the spiny burs have hardened will not remove the existing hazard.
Puncturevine (Tribulus terrestris) is a summer annual; its seeds germinate when soil moisture is good and temperatures are warm, from late spring through summer. It forms a sprawling, mat-like ground cover with opposite, pinnately compound leaves and produces small, yellow flowers. The most effective time to control Puncturevine is in late spring or early summer when seedlings are small, before it can flower and set its spiny seed capsule. Since both plants are annuals, preventing seed formation is the single most important step for long-term management.
Non-Chemical Removal Methods
Manual removal works well for small infestations or for individual plants that escape herbicide treatments. Hand-pull or hoe the plants before they set seeds, as mature burs can easily detach and spread the problem. This is best done in late winter for Lawn Burweed and in early summer for Puncturevine. Always use gloves when handling mature plants to avoid injury from the sharp spines.
Shallow tilling or hoeing is effective against Puncturevine seedlings, cutting the plant off at its taproot. Deep tilling should be avoided, however, as it can inadvertently bury dormant seeds, extending their viability. For larger patches in non-turf areas, soil solarization can be used by covering the area with clear plastic sheeting during the hottest months to generate temperatures lethal to the plants and surface seeds. In turf areas, maintaining a dense, healthy lawn by mowing at the correct height helps to crowd out the low-growing burr weeds.
Herbicide Options and Application Strategies
Chemical control involves a two-pronged approach using both pre-emergent and post-emergent herbicides. Pre-emergent herbicides are applied to the soil before the seeds germinate, creating a barrier that prevents seedlings from emerging. For the winter annual Lawn Burweed, this preventative application should be timed in the late summer or early fall (around September or October) to intercept germinating seeds. Effective pre-emergent ingredients include isoxaben, dithiopyr, and pendimethalin.
For the summer annual Puncturevine, the pre-emergent application should be made in late winter or early spring, before soil temperatures rise. Products containing trifluralin or pendimethalin are options for Puncturevine prevention. Post-emergent herbicides are used to kill existing, actively growing plants and are most effective when applied to young, small plants.
The most common and effective post-emergent products for broadleaf weeds contain a combination of auxin-mimicking active ingredients. These are often referred to as three-way herbicides, typically including 2,4-D, dicamba, and mecoprop (MCPP). Applications for Lawn Burweed are most effective during the cooler months of late fall through February, before the spiny burrs form. Puncturevine requires post-emergent application in the spring or early summer while the plant is young and actively growing. Adding a non-ionic surfactant to the spray solution can increase the effectiveness of the treatment by helping the herbicide stick to the weed’s waxy leaves.
Managing Seed Viability for Future Control
Long-term control of burr weed is difficult because their seeds persist in the soil seed bank. For Puncturevine, seeds may remain viable for up to five years, requiring annual diligence to deplete the bank. This longevity means that a single season of control will not eliminate the problem, emphasizing the necessity of preventing any mature plant from producing new seeds.
A multi-year strategy should focus on cultural practices that create an environment unfavorable for the weeds to thrive. Overseeding and soil improvement are beneficial, as a thick, dense turf canopy competes with the burr weeds for sunlight and nutrients. Appropriately timed pre-emergent herbicides must be used annually until the soil seed bank is exhausted. Monitoring the area for small seedlings that emerge late in the season and immediately spot-treating them will prevent them from reaching maturity and replenishing the seed supply.