The weed commonly referred to as “Devil Thorns” is scientifically known as Puncturevine (Tribulus terrestris). This aggressive, low-growing summer annual broadleaf weed is notorious for producing hard, woody burrs with sharp, stiff spines. These burrs easily puncture bicycle tires, injure bare feet, and harm pets. Their ability to latch onto shoes, tires, and animal fur is the primary mechanism for its widespread dispersal, making management difficult. Controlling Puncturevine requires a strategic, multi-year approach that combines manual removal, targeted chemical applications, and long-term turf health improvements.
Identifying the Target and Understanding its Life Cycle
Puncturevine is a warm-season annual that grows in a prostrate, mat-forming habit, with stems radiating out from a central taproot. The stems and leaves are often hairy, and the leaves are compound, divided into many small, oblong leaflets. The plant produces small, five-petaled yellow flowers that typically open in the morning and close by the afternoon.
The life cycle is the most important factor in its control, as the plant reproduces exclusively by seed. Puncturevine germinates in late spring or early summer once soil temperatures rise and continues to germinate throughout the summer until the first frost. It only takes about three to five weeks from germination for the plant to flower and begin producing its spiny seed burrs. Each burr contains several seeds that can remain viable in the soil for several years, creating a persistent seed bank that fuels future infestations.
Immediate Physical and Mechanical Removal Methods
Physical removal is the most direct way to control small infestations, especially before the plant produces its spiny burrs. Since Puncturevine has a simple taproot, young plants can be effectively removed by hand-pulling or with a specialized weed tool, ensuring the entire root is separated from the soil. Hand removal is most successful when the plant is small and has not yet flowered, which limits the addition of new seeds to the soil.
If the plants have already developed burrs, great care must be taken during removal, and thick gloves are highly recommended. The mature plants and any fallen burrs must be disposed of in sealed bags and removed from the property, not placed in compost, because the seeds can survive composting processes. To collect existing burrs scattered across the grass, drag sticky materials like an old piece of carpet or a specialized roller across the infested area. This mechanical action traps the burrs, effectively reducing the seed count in the soil’s surface layer.
Chemical Control Strategies
Chemical control offers a scalable solution for larger infestations using two main strategies: pre-emergent and post-emergent herbicides. Pre-emergent herbicides prevent the seeds from successfully sprouting and must be applied before the Puncturevine seeds begin to germinate. The best time for this application is in the late winter to early spring, before soil temperatures consistently reach 60 degrees Fahrenheit.
Effective pre-emergent products for turf often contain active ingredients like pendimethalin, benefin, or trifluralin. Since Puncturevine seeds can germinate throughout the warm season, a single early spring application may only provide partial control, and a second application may be necessary in late spring or early summer.
Once the plant has emerged, post-emergent selective herbicides are the correct option. Products containing 2,4-D, dicamba, or a combination thereof are highly effective against this broadleaf weed without harming most established turfgrasses. Post-emergent treatments work best when applied to young, actively growing plants; mature, hardened plants with burrs are more difficult to eliminate with chemicals.
Long-Term Turf Management for Prevention
Puncturevine thrives in areas with thin turf, dry conditions, and compacted soil. Improving the health of the grass is a powerful long-term prevention strategy. A dense, healthy lawn shades the soil surface, which inhibits the germination of Puncturevine seeds that require light to sprout.
Maintaining a taller mowing height, generally in the upper range recommended for your specific turf type, helps the grass canopy shade out the weed seedlings. Proper watering techniques are important, as the weed is drought-tolerant and thrives in dry, stressed lawns. Deep, infrequent watering encourages the turf roots to grow deeper, making the grass more competitive against the weed’s taproot.
Alleviating soil compaction through regular aeration and overseeding bare or thin areas creates a less hospitable environment for Puncturevine. Consistency with these cultural practices over several growing seasons is necessary to deplete the persistent seed bank and prevent reinfestation.