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Montana Field Guide

Montana Field Guides

Alpine Bog Laurel - Kalmia microphylla
Other Names:  Kalmia polifolia ssp. microphylla, Kalmia occidentalis

Native Species

Global Rank: G5
State Rank: S4

Agency Status
MNPS Threat Rank:
C-value: 5

External Links

General Description
Alpine Bog Laurel is a low, evergreen shrub with branched, ascending to prostrate stems that are generally 2-5 dm long and which root at the nodes. The narrowly elliptic leaves are 2-4 cm long, are opposite, and have short petioles and entire, rolled-under margins. They are dark green and glabrous above but densely gray-hairy and glandular below. Several flowers are borne on stalks that are 2-4 cm long at the stem tips. The calyx has 5 deep lobes that are 2-3 mm long, and the deep pink, bowl-shaped, 5-lobed corolla is 12-18 mm broad. There are 10 stamens. The fruit is a nearly round capsule that is 2-3 mm high; it opens by 5 slits radiating from the center.

Flowering in May.

Diagnostic Characteristics
Our only species of Kalmia. Reports of K. polifolia in the strict sense for Montana are based on larger-statured plants of K. microphylla. The diagnostic characters of club-shaped, purple trichomes along the leaf midribs and seeds >1.5 mm used to distinguish K. polifolia as treated by Ebinger (1974) and in the Flora of North America are not present in Montana material. Leaf size and shrub height which have been used to distinguish between the two species do not appear to be good morphological characters as they are highly variable, influenced by environmental conditions and overlap in the characters between the two species does occur.

Species Range

Range Comments
UT, AB, AK and YT, OR, WA, ID, MT, WY, CO, NV and CA.

Observations in Montana Natural Heritage Program Database
Number of Observations: 74

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Fens, moist to wet, organic soil of spruce forest openings and margins, margins of lakes and ponds from valley bottoms to the subalpine zone.

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Citation for data on this website:
Alpine Bog Laurel — Kalmia microphylla.  Montana Field Guide.  .  Retrieved on , from