Image by EasternColoradoWildflowers.com

Tribulus terrestris

Family: Zygophyllaceae – Caltrop Family

Annual herbs laying flat on the ground; stems 0.4” to 4” (1 to 10 cm) long

Leaves: opposite; pinnately compound; has hairs

Flowers: 5 yellow petals; 5 sepals; stamens usually 10; petals 0.12” to 0.2” (3 to 5 mm) long

Blooms in Arches National Park: August, September, October, November

Location seen: entrance road and around Visitor Center buildings

Fruits: 2-spined nutlets; spines are horn-like

Pollinators: other genera in this family are pollinated by bees

Habitat in Arches National Park: disturbed areas and open sites

Other: The genus name, “Tribulus”, is Latin for "three-pointed, a caltrop," the shape of which is suggested by the three-pronged fruit, and referring to the caltrop, a military weapon, an iron ball with projecting spikes. The species name, “terrestris”, is Latin for "on land". Put together, the scientific name can translate to “tribulation of the earth” which refers to the fact that it is not native, spreads rapidly, and has very sharp seeds that can puncture feet or tires.

This is a non-native plant.