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Montana Field Guide

Montana Field Guides

Spiny Naiad - Najas marina
Other Names:  Spiny Water-nymph

Non-native Species

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

Agency Status


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State Rank Reason (see State Rank above)
Najas marina is an aquatic plant that was first detected in Montana in 2018 at Frenchtown Pond State Park in Frenchtown (Freeman and Pfingsten 2021). Plants were discovered during surveys conducted by Montana Fish, Wildlife & Parks through the Aquatic Invasive Species Program. On-going surveys through 2021 have confirmed that plants are present in two ponds where populations appear to be abundant and healthy (Freeman personal communication). These observations along with an unpublished 2014 report in Idaho extend its range and represent the first documented locations for the Pacific Northwest (Freeman and Pfingsten 2021; U.S. Geological Survey 2022). Previously, the closest records were found in Minnesota, southeastern North Dakota, Nebraska, California, Nevada, and Utah (Freeman and Pfingsten 2021). Plants likely arrived either through non-motorized recreational activities or by waterfowl. Control strategies include containment and eradication. A conservation status rank is not applicable (SNA) because exotic plants are not a suitable target for conservation activities.

NOTE: It is important to document new occurrences by providing quality plant specimens to one of our State herbaria (University of Montana, Montana State University, or Montana State University-Billings). Herbarium specimens allow identifications to be confirmed, provide a central location for education and information sharing, are a source for conducting genetic, morphological, and ecological studies, and are the basis on which Montana's floras are written.
General Description
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Observations in Montana Natural Heritage Program Database
Number of Observations: 5

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Relative Density



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

  • Literature Cited AboveLegend:   View Online Publication
    • Freeman, S.L. and I.A. Pfingsten. 2021. First record of Najas marina (Hydrocharitaceae) for Montana and an update on the North American distribution. Phytoneuron 2021-51:1-7.
    • U.S. Geological Survey. 2022. Nonindigenous aquatic species specimen information (Najas marina), 2014 observation, Idaho. Accessed 28 October 2022.
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Citation for data on this website:
Spiny Naiad — Najas marina.  Montana Field Guide.  .  Retrieved on , from