Kalmia polifolia tends to be smaller and more low growing than Phyllodoce breweri, with which it often grows. Both species have pink to red flowers...but Kalmia requires wet boggy areas, while Phyllodoce can tolerate drier habitats.

In addition, Kalmia can be distinguished by its unique and delightful floral morphology and pollination mechanism. In freshly opened flowers, the filaments of each of the 10 stamens are arched downwards at both ends...held down at their apical ends by tension/compression on the anthers, which are tucked into 10 depressed 'saclets' on the limb of the corolla. When the anthers are mature and ready to dihisce...and an insect alights on the open corolla with sufficient force...the anthers are dislodged from their saclets, and the stamens suddenly spring up and splash pollen onto the pollinator.

In this photo the depressions formed by the 10 'saclets' on the corolla limb are visible from below. (You can also see the distinctly inrolled leaf margins, another clear way to distinguish Kalmia from Phyllodoce, which has more needle-like leaves.)