Ambrosia linearis

Perennials or subshrubs, 20-40+ cm. Stems erect. Leaves mostly alternate; petioles 0; blades mostly linear (some 1-pinnate, lobes lin­ear), 12-20(-35+) × 1(-2+) mm, bases cuneate, margins entire, abaxial faces strigillose (whitish), adaxial faces scabrellous. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0.5-1 mm; involucres cup-shaped (with black nerves), 4-6+ mm diam., strigillose; florets 12-20+. Burs: bodies pyriform to obconic, 2-4(-5) mm, strigillose, spines (4-)5-9(-13+), scattered or mostly distal, subulate, (0.8-)1-1.5 mm, tips usually uncinate.

Flowering Jul. Seasonally wet, sandy soils; 2000-2100 m; Colo.

Ambrosia linearis is in the Center for Plant Conservation´s National Collection of Endangered Plants.