Kansas Wildflowers and Grasses - Whole-leaf rosinweed

WHOLE-LEAF ROSINWEED

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Silphium integrifolium Michx.

Konza Prairie, Riley County, Kansas

Perennial

Height: 2-5 feet

Family: Asteraceae - Sunflower Family

Flowering Period: July, August, September

Stems:

Erect, occasionally branched above, nearly glabrous or velvety to rough.

Leaves:

Evenly distributed along stem, variable, mostly opposite, sometimes in whorls of 3, simple, sessile, often clasping, ovate to lanceolate, 3 to 6 inches long, 1 to 2.5 inches wide, rough above, rough to velvety or nearly smooth below; margins entire or toothed.

Inflorescences:

Heads, several, in open clusters, terminal, 2 to 4 inches wide; bracts ovate to elliptic, overlapping; margins fringed with hairs; tips usually curving outward.

Flowers:

Ray florets 15-34, 1 to 2 inches long, yellow; disk florets numerous, corollas yellow.

Fruits:

Achenes, rounded, flattened, about 1/2 inch long, winged, tipped with 2 sharp teeth, enclosing small seed.

Habitat:

Open disturbed places and roadsides, most abundant in moist, rocky soils.

Distribution:

East 2/5 of Kansas.

Uses:

Native Americans used the root of whole-leaf rosinweed as an analgesic.

Comments:

The plant contains a sticky resin, which gives it the name "rosinweed". Silphium species resemble sunflowers but differ in that their ray flowers produce seeds, while in sunflowers it is the disk flowers that produce the seeds.

Whole-leaf rosinweed