Woolly Leaf Burr Ragweed

Perennials, 10–30+ cm. Stems erect. Leaves mostly alternate; petioles 10–45+ mm; blades elliptic to ovate, 45–60(–100+) × 30–45(–75+) mm, usually 1–2-pinnately lobed (lobes ± lanceolate), bases cuneate, ultimate margins serrate, abaxial faces densely sericeous or strigillose (silver or grayish), adaxial faces strigillose. Pistillate heads clustered, proximal to staminates; florets (1–)2. Staminate heads: peduncles 1–2 mm; involucres saucer-shaped, 3.5–5+ mm diam., strigillose; florets 8–25(–40+). Burs: bodies ± pyriform to globose, 3–5+ mm, stipitate-glandular, spines 8–12+, scattered, stoutly conic, 0.5–1+ mm, tips straight. 2n = 36.

Gaertneria grayi A. Nelson, Bot. Gaz. 34: 35. 1902, based on Franseria tomentosa A. Gray, Mem. Amer. Acad. Arts, n. s. 4: 80. 1849, not Ambrosia tomentosa Nuttall 1818

Ambrosia grayi, the woollyleaf bur ragweed, is a North American species of plants in the family Asteraceae. It is native to the west-central part of the Great Plains of the United States, in the states of Nebraska, Kansas, Colorado, New Mexico, Oklahoma, and Texas.

Ambrosia grayi is a perennial herb up to 30 cm (12 inches) tall. Leaves are elliptical or egg-shaped. Flower heads are small and inconspicuous, as the plant is wind-pollinated. The heads develop into spiny burs as the seeds ripen.