Lonestar Gumweed

Annuals, 30–130 cm. Stems erect, stramineous to purple, proximally sparsely hirtellous to glabrate, distally ± hirtellous to villosulous. Cauline leaf blades ovate or ± triangular to oblong or obovate, 15–60(–90) mm, lengths 1.5–3(–4+) times widths, bases ± clasping, margins ± crenate (teeth 8–14 per cm, blunt, resin-tipped), apices obtuse to acute, faces usually hirtellous to scabridulous and glandular (glands usually in pits, sometimes sessile, seldom stipitate), sometimes glabrate. Heads in open, corymbiform to paniculiform arrays or borne singly. Involucres ± urceolate to hemispheric, 8–12 × 10–20 mm (usually subtended by leaflike bracts). Phyllaries in 4–6 series, spreading to appressed, lanceolate to linear, apices subulate, hooked to ± recurved or nearly straight, moderately resinous. Ray florets 20–27; laminae 8–12 mm. Cypselae stramineous or brownish, 3–4.5 mm, apices ± coronate to knobby, faces (outer) rugose (not transversely fissured; angles ± ribbed) or (inner) striate; pappi of 2 straight or weakly contorted, smooth (apices dilated), bristles or setiform awns 5–6 mm, equaling or surpassing disc corollas. 2n = 12.

Grindelia microcephala de Candolle var. adenodonta Steyermark, Ann. Missouri Bot. Gard. 21: 467. 1934

Grindelia adenodonta, the Lonestar gumweed, is a species of flowering plants in the family Asteraceae.

Grindelia adenodonta is native to the southern Great Plains of the United States, found only in the state of Texas.

Grindelia adenodonta grows in prairies and thickets, and along streambanks. It is an annual herb up to 130 cm (52 inches or 4 1/3 feet) tall. Leaves are narrowly egg-shaped or triangular, up to 9 cm (3.6 inches) long. The plant usually produces numerous flower heads in open, branching arrays. Each head has 20-27 ray flowers surrounding a large number of tiny disc flowers.