Silphium mohrii, known by the common names Mohr's rosinweed and shaggy rosinweed, is a species of flowering plant in the family Asteraceae. It is native to the Southeastern United States, where it is native only to northern Alabama, southern Tennessee, and extreme northwest Georgia. It occurs in prairie remnants and rocky limestone openings, often in open, dry habitats with thin soils. Because of its restricted range and severely declined habitat, it is considered a vulnerable species.
It produces heads of yellow flowers in late summer, typically flowering from August to September.
The species was first described by John Kunkel Small in 1897.
Silphium mohrii is a tall perennial distinguished by its densely shaggy-hirsute stems, inflorescence, and phyllaries, with hairs often exceeding 5 mm in length. The inflorescence is typically corymbose, bearing multiple flower heads (generally 3âÂÂ15).
It is most similar to other Silphium species with non-pinnatifid leaves, but can be distinguished by its long, shaggy pubescence and multi-headed inflorescence.
The species was first described by John Kunkel Small in 1897. In a 1999 revision of Silphium, Jennifer Ann Clevinger treated S. mohrii within Silphium sect. Silphium, a group characterized by fibrous roots and caulescent growth.