3. Grindelia squarrosa (Pursh) Dunal (curlytop gumweed)

Pl. 235 a–e; Map 984

Plants biennial or rarely short-lived perennials. Stems 10–100 cm long. Stem leaves sessile, the blades 1–7 cm long, oblanceolate to narrowly oblong, oblong, or ovate, more or less truncate to shallowly cordate at the base and slightly to moderately clasping the stem, mostly rounded to a bluntly pointed tip (the uppermost leaves occasionally sharply pointed), the margins with moderate to numerous, narrow, fine or coarse, relatively blunt teeth, rarely sparsely and inconspicuously toothed to entire, the teeth mostly with a thickened or glandular tip and lacking a bristlelike extension, the surfaces appearing strongly resinous with relatively dense glandular dots, these conspicuously darker than the surrounding leaf tissue. Inflorescences of solitary heads or loose clusters at the branch tips, occasionally a few heads also in the axils of the adjacent leaves. Receptacle 1–2 cm in diameter. Involucre 6–11 mm long, the bracts in 5–9 unequal series, strongly curled or recurved. Ray florets 20–40 or rarely absent, when present the corolla 7–15 mm long. Disc florets perfect or some of the inner and/or outer ones functionally staminate, the corollas 3.5–6.5 mm long. Pappus of 2–8 slender awns, 2.5–6.0 mm long, these barbed or less commonly smooth or nearly so, not fused at the base, not persistent at fruiting (usually shed individually as the fruit matures), off-white to straw-colored. Fruits 2–3 mm long, straw-colored to light gray or tan. 2n=12. July–September.

Introduced, scattered mostly in the northern half of the state (native range unclear; present nearly throughout the U.S. except most of the Southeast; Canada, Mexico; introduced in Europe). Pastures, railroads, roadsides, and open, disturbed areas.

The native range of this species originally probably was restricted mainly to portions of the Great Plains and the eastern edge of the Rocky Mountains (Steyermark, 1934; Cronquist, 1980), but by the early 1900s it had increased its range greatly eastward and westward. Steyermark (1963) stated that it had been documented rarely from prairies and alluvial areas, but the specimens examined during the present study originated from highly disturbed sites.

The taxonomy of the G. squarrosa complex is still not fully understood. Steyermark (1934, 1963) included a series of varieties and forms, and recognized some additional species that have been treated as varieties by some other authors. Steyermark’s var. serrulata refers to plants that correspond to var. squarrosa but tend to have somewhat narrower leaves, and it is not accepted here. The plants treated here as var. quasiperennis were treated by Steyermark as a separate species, G. perennis. Future populational studies and molecular analyses may help to elucidate the taxonomy of this group.