Puncture-vine - Tribulus terrestris
Other Names:
Puncturevine
Taprooted, mat-forming annual. Stems prostrate 10–40 cm. Herbage strigose. Leaves opposite, even-pinnate; leaflets 6 to 16, ovate, ca. 5 mm long. Flowers: petals yellow, 3–5 mm long; stamens 10; ovary 5-lobed. Fruit a schizocarp, each 2-seeded mericarp with two large spines 2–6 mm long and numerous fine bristles (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).