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Montana Field Guide

Montana Field Guides

Larger Canadian St. John's-wort - Hypericum majus

Native Species

Global Rank: G5
State Rank: SNR

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 8

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General Description
Stems ascending but decumbent, simple or branched, 5–25 cm high. Leaves 10–25 mm long, lanceolate with rounded tips. Flowers: sepals attenuate-lanceolate, 4–7 mm long; petals as long as sepals. Capsule 4–6 mm long with yellow seeds (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Diagnostic Characteristics
Montana has 3 native and 1 exotic species of Hypericum. All have leaves that are opposite, sessile, entire, and dotted with translucent glands. Hold a leaf up to the sunlight and see the glands.

Larger Canadian St. John’s-wort - Hypericum majus, native and desirable
* Mature plants are 5-25 cm tall, grow decumbant.
* Smaller flowers with 5-yellow petals not outlined by black glands and about as long as sepals.
* Habitat along rivers, ponds, and lakes in valley and montane zones.

Western St. John’s-wortHypericum scouleri, native and desirable
* Mature plants are 5-60 cm tall.
* Large flowers with 5-yellow petals outlined by black glands.
* Sepals are ovate with rounded tips and amber veins.
* Rhizomatous and stoloniferous.
* Habitat is moist to wet areas in meadows, along streambanks, and on ledges from the valleys to the alpine zones.

Common St. John’s-wort - Hypericum perforatum, exotic and noxious
* Size: Mature plants are 25-75 cm tall.
* Flowers: 5-yellow petals outlined by black glands and showy yellow stamens.
* Sepal: 5 linear-lanceolate with acute tips.
* Branches: reddish-colored that help make the plant more noticeable in fall.
* Fruit: a 3-valved capsules with many, tiny seeds.
* Roots: taprooted and rhizomatous.

Tinker’s-penny - Hypericum anagalloides, native and desirable
* Mature plants are 2-12 cm tall, grow along the ground, and root at leaf nodes.
* Smaller flowers with 5-yellow petals not outlined by black glands and slightly longer than sepals.
* Habitat of wetlands and wet soil in meadows along streams in montane and subalpine zones.

Range Comments
BC to QC south to WA, CO, IL and PA (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Habitat

References
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Citation for data on this website:
Larger Canadian St. John's-wort — Hypericum majus.  Montana Field Guide.  .  Retrieved on , from