Puncturevine, scientifically known as Tribulus terrestris, is a common weed recognized by its distinctive appearance and, more notably, its spiny seed pods. These burrs, often called “goat’s heads,” readily attach to anything that brushes against them, leading to its various common names. Understanding this plant is key to effective management.
Identifying Puncturevine
Puncturevine (Tribulus terrestris) is a summer annual that forms dense, prostrate mats from a central taproot. Its hairy stems can radiate outwards up to six feet. The leaves are pinnately compound, appearing fern-like with small, oval leaflets. Small, bright yellow flowers with five petals emerge from leaf axils, typically opening on sunny mornings.
The plant’s most distinctive feature is its woody, spiny seed pod, or bur. These gray to yellowish-tan burrs, about 1/5 to 2/5 of an inch in diameter, break into five wedge-shaped segments at maturity. Each segment bears two to four sharp, rigid spines, which are the source of its common names.
Where Puncturevine Grows
Puncturevine (Tribulus terrestris) is an introduced species, native to southern Europe, Asia, and Africa, now widely distributed across warm temperate and tropical regions. It thrives in disturbed areas with poor, dry, compacted soils and full sun exposure. Common habitats include roadsides, railroad tracks, neglected gardens, pastures, and pavement cracks. The plant reproduces solely by seed, which germinates from spring through fall, especially after rain. Seeds spread easily by attaching to vehicle tires, shoes, clothing, animal fur, and agricultural equipment, facilitating rapid colonization.
The Problems Caused by Puncturevine
Puncturevine is a nuisance due to the sharp, durable spines on its seed pods. These burrs can puncture bicycle tires, injure bare feet, and harm pet paws. In agricultural settings, the spiny burrs damage farm equipment and contaminate hay, potentially injuring livestock. The plant can also be toxic to livestock, especially sheep, if consumed in large quantities, leading to conditions like photosensitivity or nitrate poisoning. Beyond physical harm, puncturevine aggressively competes with desirable plants for water and nutrients, particularly in dry conditions, reducing crop yields and native plant diversity.
Effective Control and Removal Methods
Preventing seed production is a primary strategy for managing puncturevine. Removing plants before they flower and set seed significantly reduces new seedlings in subsequent years. Cleaning shoes, clothing, and vehicle tires after being in infested areas also helps prevent inadvertent seed spread.
Manual Removal
Manual removal is effective for small infestations. Hand-pull or hoe plants, ensuring the taproot is severed below the soil surface, ideally when the soil is moist. If plants have already produced seeds, collect all dropped burrs by sweeping, raking, or patting the ground with an old piece of carpet. Shallow tilling (one inch or less) can control young plants, but deeper tilling is not recommended as it may bury seeds, allowing them to remain viable for several years.
Cultural Control
Cultural control methods focus on creating an unfavorable environment for puncturevine. Applying a four to six-inch layer of mulch can suppress germination by blocking sunlight and discouraging new growth. Establishing healthy, competitive cover crops or desirable perennial plants can also help by shading the soil and outcompeting puncturevine seedlings for resources.
Chemical Control
Chemical control can supplement other methods. Pre-emergent herbicides, applied in late winter to mid-spring before seeds germinate, offer partial control. Products containing oryzalin, benefin, or trifluralin are suitable for this.
For established plants, post-emergent herbicides like 2,4-D, dicamba, or glyphosate are effective. Glyphosate is non-selective, killing most plants it contacts. In contrast, 2,4-D and dicamba are broadleaf-selective and can be used in lawns without harming desired grasses. Always read and follow product label instructions carefully for safe and effective application.