Grevillea hortiorum Olde (Proteaceae: Grevilleoideae: Hakeinae), an uncommon species from winter-damp woodlands in the Avon Wheatbelt, south-west Western Australia

Grevillea hortiorum Olde is here described as a new species. It is a member of the Triloba Group sensu Flora of Australia, based on shared morphological characters, and it may be related to Grevillea acrobotrya Meisn. Numerous morphological differences distinguish it as a species, but its relationships have not been tested with phylogenetic data. Subsequent to its initial discovery, when it was thought to be rare, both its distribution and knowledge of populations have been greatly expanded, almost exclusively due to the efforts of its eponymous collectors. It was initially thought to be uncommon and associated with open wandoo woodland, but later collections have been gathered in open heath as well. An interim key to Grevillea hortiorum is provided.