General: Prickly Russian Thistle (Salsola tragus) is an invasive weed that does well on disturbed soils. When dried out and rolling across the ground on a windy day, everyone recognizes tumbleweeds. When green, the plant grows long, upward and outward stretching stems that curl up into a large ball or basket (3 to 4 ft diameter) as they dry out. The main stem breaks free from the root when the seeds are ripe, allowing the plant to blow and tumble across the landscape. The non-native species does poorly in competition with native species on undisturbed soils.

Prickly Russian Thistle is a common component of vegetation communities on disturbed soils throughout lower-elevation urban and desert areas in the Lower Sonoran (Creosote-Bursage Flats) and Upper Sonoran (Mojave Desert Scrub and Pinyon-Juniper Woodland) life zones. The species can also be found into the Transition (Yellow Pine Forest) and Canadian (Pine-Fir Forest) life zones to about 8,500 feet elevation in disturbed areas.

Family: Goosefoot (Chenopodiaceae).

Other Names: Tumbleweed

Plant Form: Annual forb that grows long, outward stretching stems that curl up into a large ball or basket (3 to 4 ft diameter) as they dry out.

Height: About 3 to 4 ft.

Stems: Main stem at base to about 1/2 inch diameter. Branches many, thin. Stem green with red or purple stripes when young, aging to yellowish. Stem breaks free when seeds are ripe.

Leaves: Blades 1/3 to 4 inches, thread-like, becoming sharp pointed.

Flowers: Blooms summer through fall. Flower inconspicuous, in leaf axils; look like saucers with pinkish center.

Seeds: Hard and well protected with 3 stout spines. Stem breaks free when seeds are ripe and the stems are curled into a loose ball; wind-blown balls spread seeds across the landscape.

Habitat: Dry, well-drained sandy, gravelly, and rocky soils on upper bajadas and moderate slopes in the lower mountains.

Elevation: Below sea level to about 8,500 ft, but usually found in lower-elevation areas.

Distribution: Widespread throughout North America; native to Eurasia.

Comments: Called tumbleweeds because the mature plants blow on the wind to disperse seeds. A similar species, Russian Thistle (Salsola kali) occurs in California, Arizona, and several east coast states.