Roldana is a genus of large herbs and subshrubs belonging to the groundsel tribe (Senecioneae) within the daisy family, Asteraceae (order Asterales). The genus was described by Pablo de La Llave in 1825 and is native primarily to Mexico and Central America, with a few species extending into the southwestern United States. The genus encompasses roughly 40–80 species and is closely allied with the large and cosmopolitan genus Senecio; most members of Roldana were formerly classified within Senecio and were progressively transferred as phylogenetic work clarified the boundaries between the two groups.
Plants in the genus are typically robust, forming large leafy herbs or semi-woody subshrubs with broad, often palmately lobed or toothed leaves. They bear characteristic composite flower heads arranged in corymbs, with yellow ray and disc florets typical of the Senecioneae tribe. Roldana petasitis, the velvet groundsel, is among the best-known members and is widely cultivated as an ornamental for its large felted leaves and bright yellow flowers.
Etymology
The genus name Roldana was established by Pablo de La Llave in 1825 in Novorum Vegetabilium Descriptiones. The name honours Roldán, though the exact eponym is not specified in the original description.
Distribution
Roldana species are native to southwestern North America, with the centre of diversity in Mexico and a range extending through Central America; a small number of species reach the southwestern United States. Several species have become naturalized outside this native range.
Taxonomy Notes
Roldana was segregated from the large, polyphyletic genus Senecio (tribe Senecioneae, family Asteraceae). Most species in the genus were historically treated as Senecio and later transferred to Roldana as molecular and morphological studies redefined generic limits within the groundsel tribe. Some former Roldana names are now regarded as belonging to other genera such as Trixis. The species Roldana oaxacana, R. sartorii, and R. cristobalensis are currently accepted as varieties of R. petasitis.
