Puncturevine (Tribulus terrestris) is an invasive annual plant that challenges landscapes and agriculture across many regions. This weed is also known as Goat’s Head or Devil’s Weed, names that refer directly to its most notorious characteristic: the fruit. The fruit develops into a small, woody burr armed with sharp, stiff spines capable of puncturing bicycle tires and causing painful injuries to people and pets. Its rapid growth and prolific seed production necessitate immediate and sustained control efforts to prevent widespread establishment.
Key Features for Identifying Puncturevine
Puncturevine is easily recognizable by its prostrate, mat-forming growth habit, allowing it to spread quickly and densely across the ground surface. Stems radiate outward from a central taproot, often creating large patches in disturbed soils, roadsides, and lawns. The leaves are opposite and pinnately compound, divided into several pairs of small, oval-shaped leaflets that give the foliage a fine, feathery appearance.
The plant produces small, solitary flowers in the leaf axils, typically featuring five bright yellow petals. These flowers are often inconspicuous, but their presence indicates the imminent formation of the fruit. After pollination, the flower develops into a spherical fruit that splits into five wedge-shaped sections, known as burrs.
Each burr is exceptionally hard and woody, housing several seeds and bearing two or more rigid, sharp spines that resemble a goat’s head. These burrs are the primary means of identification and dispersal, often sticking to shoes, animal fur, or vehicle tires. Their durability allows them to remain a persistent hazard long after the parent plant has died.
Understanding the Puncturevine Life Cycle
Puncturevine functions as a summer annual weed, completing its life cycle within a single growing season and dying off with the first hard frost. Germination typically begins in late spring or early summer when soil temperatures consistently warm above 60 degrees Fahrenheit. This timing dictates the window for effective pre-emergent herbicide application.
Once established, the plant exhibits rapid vegetative growth, quickly forming sprawling mats. This development is followed by prolific and continuous seed production throughout the warmer months. A single plant can produce hundreds or thousands of burrs during its lifetime, ensuring a large seed bank for future seasons.
The burrs play a significant role in the plant’s survival, as their tough, spiny exterior protects the seeds and facilitates physical dispersal. Seeds within the burrs can remain dormant and viable in the soil for several years, sometimes up to seven or more. This long viability means control efforts must be sustained over multiple seasons to deplete the existing seed bank.
Immediate Control Strategies
Controlling Puncturevine relies on timely intervention, ideally before the plant produces hardened burrs. For small infestations, mechanical removal through hand-pulling or hoeing is highly effective, provided the work is done while the plant is young and flowering. Pulling the plant ensures the removal of the taproot, which prevents regrowth.
When hand-pulling, place the uprooted plants directly into a sealed bag for disposal to prevent fallen burrs from contacting the soil. If plants have already developed burrs, a detailed cleanup of the soil surface using a rake or shop vacuum is necessary to remove the persistent seeds. Leaving burrs on the ground is equivalent to reseeding the area.
For larger, heavily infested areas, soil solarization can eliminate both existing plants and surface-level seeds. This non-chemical method involves covering the moist, cleared soil with clear plastic sheeting during the hottest months of summer. The trapped solar heat raises soil temperatures high enough to kill viable seeds and remaining plant material over four to six weeks.
Chemical control offers two primary approaches depending on the plant’s life stage. Pre-emergent herbicides prevent seeds from germinating and establishing roots. These chemicals must be applied in early spring, just before the soil reaches the 60-degree Fahrenheit germination temperature, providing a barrier against new weeds.
Post-emergent herbicides are applied directly to actively growing plants. Herbicides containing active ingredients like 2,4-D or dicamba are commonly used for broadleaf weed control, including Puncturevine. However, the effectiveness of these sprays decreases significantly once the Puncturevine matures, develops extensive mats, and begins forming woody burrs. Once the stems are woody, sprays may only scorch the foliage without killing the entire plant, allowing seeds to mature. The most successful strategy combines a well-timed pre-emergent application followed by spot treatments with a post-emergent spray on any emerging plants. Always follow manufacturer’s instructions regarding application rates and safety precautions.
Long-Term Prevention and Site Management
After removing existing Puncturevine, the focus shifts to preventing new infestations from the dormant seed bank. The most effective long-term strategy is altering the environment to make it less favorable for germination, as Puncturevine thrives in bare, disturbed soil.
Applying a thick layer of organic mulch (three to four inches deep) suppresses seed germination by blocking sunlight and moderating soil temperature. Establishing a dense, desirable ground cover or turfgrass can also outcompete Puncturevine seedlings for light and nutrients. Consistent irrigation and fertilization promote healthy competition and discourage weed establishment.
Ongoing monitoring is necessary since seeds may sprout intermittently. Regularly inspect previously infested areas and perform immediate spot treatments, either by hand-pulling or using a targeted herbicide, as soon as new seedlings appear. Catching these plants before they produce a burr is the most effective way to exhaust the seed bank over time.
Preventing the physical transport of burrs into clean areas is also important. Always check and clean vehicle tires, bicycle treads, and pet fur after traversing an infested area. Even a few carried seeds can quickly start a new, localized infestation.