1166. <i>Helianthus occidentalis</i> Riddell

Summary Helianthus occidentalis Riddell (Compositae: Heliantheae: Helianthinae) is described and illustrated. The species' placement in the genus is commented on, as are the differences in infrageneric placement of the other species Heiser originally grouped H. occidentalis with. Notes are provided for the species' cultivation, propagation, likely pests and diseases, and availability. A full synonymy is given, along with type citations and known presence of type material, together with relevant notes. Selected illustrations of the species are cited, and statements of the species' distribution, habitat and ecology, phenology, etymology, conservation status and vernacular names provided. A very brief biographical note of John Leonard Riddell, the collector and author of the species, is offered. Discussions include observations on the inclusion of H. dowelliannus M.A. Curtis in synonymy, aspects of publication of Riddell's name, and one nomenclatural irregularity that has appeared in the literature. The chocolate aroma of the flowering capitula is commented on (especially as it is also found in other species of Helianthus ), as are other smell‐types within the tribe Heliantheae.