Silphium glutinosum
Castanea 66: 183, figs. 11, 12A–C. 2001.
Plants caulescent 80–150 (–180) cm; fibrous-rooted. Stems terete, scabrous, stipitate-glandular. Leaves: basal caducous; cauline usually opposite, rarely alternate, petiolate or sessile; blades lanceolate to ovate, 3–22 × 1–12 cm, bases attenuate to rounded, margins toothed or entire, apices acute to acuminate, faces scabrous, stipitate-glandular. Phyllaries 19–23 in 3–4 series, outer appressed to reflexed, apices acute to obtuse, abaxial faces scabrous, stipitate-glandular. Ray-florets 8–16; corollas pale-yellow. Disc-florets 50–70; corollas pale-yellow. Cypselae 6–8.5 × 4–7 mm; pappi 0.5–2 mm. 2n = 14.
Phenology: Flowering summer–early fall.
Habitat: Limestone glades, along rocky streams
Elevation: 100–300 m
Discussion
James Allison (in protologue) suggested that Silphium perplexum is a hybrid between S. glutinosum and S. integrifolium. It has glandular hairs on its stems, leaves, and phyllaries as in S. glutinosum; it is also found on chalk, has taller stems, larger leaf blades, and deeper yellow corollas. Further study is needed to determine its status.
Selected References
None.
Lower Taxa
"broader" is not a number.