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Montana Field Guide

Montana Field Guides

Glaucous Rattlesnake-root - Prenanthes racemosa

Native Species

Global Rank: G5
State Rank: SU
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
A single collection of Prenanthes racemosa variety multiflora that came from "an undetermined station in Montana" was included in the Vascular Plants of the Pacific Northwest-Volume 5 (Cronquist 1955). This provided the reason for its inclusion in the Vascular Plants of Montana (Dorn 1984) and the Manual of Montana Vascular Plants (Lesica et al. 2012). Interestingly it was not included in the Flora of Montana (Booth 1966), and further this collection has not been found. This plant is also reported for Montana based on Bogler's treatment in the Flora of North America (2006); but the supporting documentation could not be found. The Montana Natural Heritage Program retains an observation that was listed as an associated species found with Lonicera caerulea var. cauriana (RM 914262 herbarium specimen by Erwin Evert). In Montana Prenanthes racemosa is given a conservation status of unrankable (SU) because a resolution to these potential occurrences has not been found. A visit to the site where Evert collected Lonicera caerulea is needed.
General Description
PLANTS: Perennial plants that grow from rhizomes. Stems are erect, usually simple, have milky sap, and are 50–120 cm tall. Stems have long, coarse, and stiff (hispid) hairs above and no hairs (glabrous) below.

LEAVES: Basal and alternately arranged on stem. Leaves are simple with entire to dentate margins, 7–40 cm long. Upper leaves are lanceolate in shape and sessile. Lower leaves are oblong.

INFLORESCENCE: White to pinkish flowers occur in heads that are arranged in racemes to narrow panicles. Involucre is narrowly campanulate, 11–12 mm high. Involucral bracts are arranged in 2 rows and setose. The outer row is short; inner row is linear-lanceolate, scarious margined. Receptacle is flat and naked. Flower heads composed only of 9-29 ligulate florets. Ray petals are white to pink, 7–13 mm long. Fruit is an achene.

Diagnostic Characteristics
Glaucous Rattlesnake-root - Prenanthes racemosa, unconfirmed presence in Montana
*Leaves: Mid-stem leaves are sessile to cordate-clasping.

Arrow-leaf Rattlesnake-root - Prenanthes sagittata
*Leaves: Most stem leaves have petioles.

Observations in Montana Natural Heritage Program Database
Number of Observations: 1

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Relative Density



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

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Glaucous Rattlesnake-root — Prenanthes racemosa.  Montana Field Guide.  .  Retrieved on , from