Arnica louiseana ranges from 5 to 20cm (2 to 8in) when full grown with simple, unbranched above ground stems.[3] It grows from rhizomes, creeping underground stems.[4] Plants usually have pairs of cauline leaves, ones that attach to the stems rather than to the base of the plant, but are crowded towards the base of the stems particularly in short plants. Each stem will have one to three pairs of leaves that are elliptic, oblong, or ovate-lanceolate in shape. They measure 1.5 to 7.5cm in length and just 0.5 to 2cm wide. Usually the edges of the leaves are smooth, however they can be denticulate, very finely toothed, or slightly undulate, a wavy edge.[3]
Usually plants will have just one flowering head, but on occasion they may have two or three. When blooming they nod, hang downward rather than facing upwards.[3] Both the ray and disk flowers are light yellow in colour.[5] Each flowering head will have seven to ten ray flowers,[3] each producing a petal 12–14mm long.[5] When blooming the flowers are noticeably fragrant.[5]
The seeds are brown cypselae, each 3–5mm with a white pappus, the parachute for distributing the seed like a dandelion.[3]
The species name was selected for the species by Farr because the specimens were found on Mt. Fairview near Lake Louise in Banff National Park.[5] It is known by the common names of Lake Louise arnica or snow arnica.[3] In French it is called arnica du lac Louise.[6]
Range and habitat
Arnica louiseana is endemic to Canada and only grows in British Columbia and Alberta. There its range extends across 20,000 to 200,000km2 (7,700 to 77,200sqmi). The total number of populations is estimated at 21 to 80.[1] All documented occurrences in Alberta are found in the southwest of the province in the Rocky Mountains.[7] Its habitat is between 1,800 and 2,100m (5,900 and 6,900ft) in elevation.[3]
This species grows on exposed slopes in the alpine tundra and on calcareous rock slides.[3]
Conservation
In 2021 the conservation organization NatureServe evaluated the species as vulnerable (G3) due to it being an endemic species that is not found in large numbers. No information was available about population changes for the species, but most populations are found in protected areas.[1]
Acadia University; Université de Montréal Biodiversity Centre; University of Toronto Mississauga; University of British Columbia (2025). " - Database of Vascular Plants of Canada (VASCAN)". Canadensys. Archived from the original on 9 September 2021. Retrieved 16 June 2025.
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