Keyed using Kershaw & Allen 2020 which follows the 2014 Flora of N. America treatment that elevated P. hippiana var. effusa to species level, thus P. effusa.

-abundant cottony hairs on both sides of leaves (= a gray-aspect plant)
-side leaflets often unevenly paired, and secondary leaflets can be interspersed
-averages 4-9 teeth/side of leaflet, with a max. distal tooth edge of ~ 4mm
-upper leaflet pair not generally decurrent
-flowering stems tend to have relatively more cauline leaves (2-6+)
-epicalyx bracelets are relatively sparsely hairy and tend to be nearly hairless at the tips, have white cottony hairs towards the bases, generally don't have sericeous hairs, and are slender, linear-shaped and shorter - this all relative to the sepals

This plant had a few departures from the FNA description, but I'm not going to quibble since it's possible the FNA author didn't have a lot of Canadian material to examine:
-styles measured in at ~2.5 mm instead of the max. given of 2.1 mm
-one of the terminal leaflets measured ~4 cm, where the max. length given for leaflets is 3 cm
-the inflorescence looks to have > than 30 flowers
http://floranorthamerica.org/Potentilla_effusa

P. hippiana has these contrasting features:
-upper surface of leaves tend to be green, without cottony white hairs, so the leaves appear bicolor and the plant has a green aspect
-leaflets are generally evenly paired and without secondary leaflets
-average of 7-12 teeth/side (same max. distal edge of 4 mm)
-upper leaflet pair generally decurrent
-cauline leaves generally fewer (1) 2-3
-epicalyx bractlets tend to be more densely hairy throughout, even out to the tips, with abundant sericeous hairs, and relatively fewer or no white cottony hairs; shape a little wider and a little longer relative to P. effusa, but length still < sepals
-overall the plant & its parts tending to be a bit larger than P. effusa (larger leaflets to 6 cm max. for example)
-style max. length 2.5 mm
http://floranorthamerica.org/Potentilla_hippiana

2024-03-22 Update: The P. effusa plant in this obs. keys very nicely but it turns out that many AB plants are intergraded with P. hippiana and so the two become hard to separate, unlike out east where it is much clearer. Oh well!

Collected by permit.