Gumweeds are annual, biennial, or perennial herbs, sometimes woody at the base, with alternate leaves, which are more or less resinous-dotted with small pits. The plants have several or numerous medium-sized to rather large heads, with the disk seldom being less than 1 cm wide. The flowerheads have rays in most of our species, or occasionally they have diskflowers only. The rays amount to mostly 10-45, and are female and fertile. The involucre is more or less resinous or gummy, its bracts firm, partly overlapping or almost equal in length. The receptacle is flat or convex, and is naked. The disk flowers are yellow, the inner ones and often also the outer ones sterile. The anthers are entire or nearly so at the base. The style branches are flattened, with marginal stigma-bearing lines, are hairy on the outside, and are mostly lance-linear. The achenes are flattened to almost 4-angled, and barely nerved. The pappus consists of 2 to several firm deciduous awns, often somewhat edged with small, sharp teeth. The genus is named for David Hieronymus Grindel, 1776-1836, Russian botanist.
Guide to Identify Presented Species of Genus Grindelia
STEM HAIRLESS
G. squarrosa – Curly-cup Gumweed Aromatic plant, 20-60 cm tall, hairless, with many branches. Dry, open places.
Flowerheads yellow, 2-3 cm wide, with sticky, backward curling involucral bracts.
Leaves alternate, oblong, 10-35 mm long, 6-12 mm wide, with resinous glands.
