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Montana Field Guide

Montana Field Guides

Flowering-rush - Butomus umbellatus

Noxious Weed: Priority 2A
Aquatic Invasive Species
Exotic Species (not native to Montana)

Global Rank: G5
State Rank: SNA
* (see State Rank Reason below)

Agency Status
MNPS Threat Rank:
C-value: 0

External Links

State Rank Reason (see State Rank above)
First collected in Montana in 1964. Known from the Flathead Drainage downstream to Noxon Reservoir; and Salmon Lake.
General Description
Perennial scapose herb from a fleshy rhizome. Herbage glabrous. Leaves mainly basal, 2-ranked, ascending to erect, linear, 4–8 mm wide. Inflorescence an umbel enclosed by 3 ovate, purplish bracts, reflexed at anthesis; pedicels unequal, 1–9 cm long; scape 3-angled, 50–100 cm. Flowers perfect, regular; sepals 3, green; petals 3, pinkish, 8–12 mm long; stamens 9; ovaries superior; pistils 6. Fruit many-seeded, beaked follicles, 8–10 mm long (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Flowering June-August

Range Comments
Introduced to much of northern U.S. and adjacent Canada; native to Eurasia. Known from Lake and Flathead counties (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Summary of Observations Submitted for Montana
Number of Observations: 54

(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)

Marshes, wetlands and slow-moving water along riverbanks.

Reproductive Characteristics
Reproduces and spreads by seeds and vegetatively via rhizomes and bulbils.

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Citation for data on this website:
Flowering-rush — Butomus umbellatus.  Montana Field Guide.  .  Retrieved on , from