Best considered the ‘western’ Winged kelp (in contrast to its eastern counterpart Alaria esculenta (Linnaeus) Greville), this species is reasonably distinct in the BC flora having a well-developed midrib (Image A) running the length of the simple vegetative blade that arises from a hapteral holdfast (Image B). In combination with the previous features, the production of the sporangial sori on paired blades (sporophylls) arising from the stipe serve to characterize this species (Image B).
This species appears confined to the NE Pacific (I suspect a collection in Lane et al. (2007) from the Arctic was mislabeled). It extends from the upper intertidal (exposed sites) to the shallow subtidal and can dominate the lower intertidal in some areas.
This species is highly variable in morphology and was considered to be a number of distinct species in BC prior to Lane et al. (2007). A personal favourite was the Alaria nana H.F.Schrader morphology – tiny plants growing in the upper intertidal at exposed locations (Image C). Although the decision of Lane et al. (2007) has been controversial to some, a recent study based on whole genomes did not alter this perspective (Bringloe et al. 2021) and we continue to recognize a single species at this time. While individuals in some habitats can have elongate stipes (Image D), these stipes are quite pliable. In contrast the closely allied Pterygophora californica Ruprecht has a stiff and more robust stipe and the central midrib on its blade is only weakly developed.
Image A. Simple blades characterized by a distinct central midrib (subtidal (2 m) on rock, Murchison I. NE site, Gwaii Haanas, BC; EGWS000485).
Image B. Simple blades characterized by a distinct central midrib, anchored by a hapteral holdfast (mostly removed on this press) and producing paired sporophylls from the stipe (subtidal (1.5 m) on rock, Whiffin Spit, Sooke Harbour, Vancouver Island, BC; GWS006396).
Image C. Alaria nana H.F.Schrader morphology growing upper intertidal on rock (Ramsey Island (point adjacent Kloo Rock), Gwaii Haanas, BC; GWS013140).
Image D. Subtidal (1.5 m) individuals in an area of current with elongate stipes (Faraday Island, Gwaii Haanas, BC; GWS013140).