Goat Head Weed Seeds

Fact sheet for Goathead ( Tribulus terrestris ), a member of the caltrop family (Zygophyllaceae), including images, botanical description, weedy characteristics, and strategies for eradication Goat Head Weed Seeds Goatheads (puncturevine) are invasive, annual weeds that produce hundreds of spiky seeds on each plant. The seeds can flat a bicycle tire or injure a dog’s paw. If you walk

Northern Arizona Invasive Plants

a northern arizona homeowner’s guide to identifying and managing invasive plants


Common name(s): Goathead, puncturevine

Scientific name: Tribulus terrestris

Family: Caltrop family (Zygophyllaceae)

Reasons for concern: This plant easily outcompetes native plants, resulting in dense monocultures and a reduction in native plant diversity very important to wildlife and pollinators. The seeds germinate quickly and can lie dormant in the soil for many years, prolonging the life of an established population. Sharp burrs cause serious injury to people, pets, wildlife, bicycle and vehicle tires, and livestock, and are easily spread by vehicles, pedestrians, and animals, resulting in even larger populations.

Classification: Non-native. Included on the Arizona Noxious Weed List as a Class C noxious weed, which means it is widespread and “may be recommended for active control based on risk assessment.”

Botanical description: Mat-forming, fast-growing broadleaf plant.

Leaves: Each small, hairy leaf is subdivided into 4 to 8 pairs of smaller leaflets, opposite each other on stems.

Stem(s): Grows low to the ground, forming dense mats 2 to 5 feet in diameter. Can grow almost erect in dense vegetation. Hairy, trailing stems radiate out from a central point at the taproot.

Flowers: Bright yellow, with five petals. Appear in the axil, where the leaf meets the stem. Open only in the morning. Blooms July through September.

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Seeds: Seedpod is a cluster of 5 flat spiny burrs, containing up to 5 seeds. It breaks apart at maturity.

Roots: Deep taproot branching into network of fine rootlets.

Native to: Southern Europe

Where it grows: Dry or gravely sites. Roadsides, waste places, pastures, fields, railroad tracks. Prefers dry, well-drained, sandy sites below 7,000 feet in elevation.

Life cycle: Summer annual

Reproduction: By seed Goathead habit.

Weedy characteristics: Goathead thrives in hot and dry conditions where other plants cannot. Its dense mat smothers out other species. It can start flowering within 3 weeks of germination, and continues to flower all summer. Depending on the moisture available, it typically produces 200 to 5,000 seeds in one growing season. Seeds can remain dormant in the soil for 5 years. Its roots are hard to remove.

Control strategies: Do not let them flower and go to seed! Prevent the seeds from spreading. Seedlings are easy to remove by hand pulling, and older plants can be pulled or dug out. Rake or sweep up any burrs that may have dropped. Tilling can be effective before seed production. Frequently monitor a population for new plants. Plant desirable native species to outcompete invasives. Herbicides are effective on small, actively growing plants. Contact your local county extension office for more information on chemical control.

Images: Click on an image to enlarge and see the image citation.

Goat Head Weed Seeds

Goatheads (puncturevine) are invasive, annual weeds that produce hundreds of spiky seeds on each plant. The seeds can flat a bicycle tire or injure a dog’s paw. If you walk or ride your bicycle across a goathead, seeds may stick in the sole of your shoe or in your bike tire.

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The thorns “hitch a ride” on your shoe or tire. Maybe they will drop off, or you’ll pull them out, leaving spiky seeds along the side of the trail. Thus does this evil weed spread.

Most of Parley’s Trail is currently goathead-free. But, there are a couple bad patches in the western section of the trail, and some near Tanner / Parley’s Historic Nature Park. Parley’s Trail also connects to the Jordan River Trail which has a significant (infamous?) infestation.

Volunteers are needed to adopt sections of the trail:

Pick a segment to adopt (see trail segment maps). Please choose a section where you can commit to walk (or bike VERY slowly) about every 2 weeks from early April to the end of September. We have mapped out 17 sections.

Pull out goatheads yourself — we’ll provide a tool. You can also pull them (carefully) with your bare hands, and throw them into the trash. A plastic grocery store bag is sufficient for the occasional plant or two.

Get a few friends to help. Coordinate a small (socially-distanced) pulling party for small / medium infestations. You’ll need a few heavy-duty trash bags.

Send an SOS to the PRATT board for larger infestations so we can get additional help.