Slender Marsh Blue Grass

Poa paludigena Fern. & Wieg.

Poa paludigena line drawing
Britton, N.L., and A. Brown (1913); downloaded from USDA-Plants Database

Monocotyledoneae (Monocots)
Poaceae (Grass Family)
State Protection
Listed as Endangered by New York State: in imminent danger of extirpation in New York. For animals, taking, importation, transportation, or possession is prohibited, except under license or permit. For plants, removal or damage without the consent of the landowner is prohibited.
Federal Protection
Not Listed
State Conservation Status Rank
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
Vulnerable globally, or Apparently Secure - At moderate risk of extinction, with relatively few populations or locations in the world, few individuals, and/or restricted range; or uncommon but not rare globally; may be rare in some parts of its range; possibly some cause for long-term concern due to declines or other factors. More information is needed to assign either G3 or G4.


Did you know?

Despite its broad distribution, this grass is considered globally rare since so few populations are known. The epithet paludigena refers to its habitat preference as it means "born of the marsh."

State Ranking Justification

There are five known populations and 13 historical populations. All of these known populations are quite small and in wetland habitats that may be susceptible to run-off or invasive species. With a somewhat specific habitat type (open to slightly wooded calcareous wetlands), there is a limited amount of available habitat. This plant has likely always been rare in New York.

Short-term Trends

All of our extant occurrences have only been surveyed once so there is no data on their trend over the last 30 years. They seem to be in relatively stable envirionments so we would not expect large fluctuations over time.

Long-term Trends

This grass has never been common in the state with only thirteen occurrences known. However, many of the historical localities have been searched and less than fifty percent of these populations have been relocated. This decline in known populations has been caused in part by habitat destruction of supporting wetlands but other factors may be responsible such as changes in water regimes and difficulty in surveying and recognizing this plant.

Conservation and Management


This plant is likely susceptible to natural succession (i.e. open to slightly wooded wetlands naturally progressing to shrub-dominated wetlands with little sunlight reaching the ground layer). Changes in the surrounding landscape that might affect the hydrology of these sites, and thereby impact populations of this grass.

Conservation Strategies and Management Practices

The open wetlands where this plant occurs should be periodically monitored for changes in succession that might reduce its habitat. The open wetland habitat should be maintained.

Research Needs

Experiments could be done to study its response to light and succession. Knowing how long this species survives witin the seed bank may allow for easier management and ease concern about changing habitats.



This is a plant of open to forested circumneutral wetlands, including swamp margins, boggy openings within forested swamps, seepage springs, tamarack swamps, etc. (New York Natural Heritage Program 2005). Boggy woods and swamps (Rhoads and Block 2000). Bogs and wet woods (Gleason & Cronquist 1991). Bogs, swamps, and wet woods, usually in sphagnum or other moss (Voss 1972). Sphagnum bogs, tamarack swamps, cold spring heads, etc. (Fernald 1970).

Associated Ecological Communities

  • Hemlock-hardwood swamp* (guide)
    A swamp that occurs on mineral soils and deep muck in depressions which receive groundwater discharge. These swamps usually have a fairly closed canopy (70 to 90% cover), sparse shrub layer, and low species diversity. The tree canopy is typically dominated by eastern hemlock and co-dominated by yellow birch and red maple.
  • Marsh headwater stream* (guide)
    The aquatic community of a small, marshy perennial brook with a very low gradient, slow flow rate, and cool to warm water that flows through a marsh, fen, or swamp where a stream system originates. These streams usually have clearly distinguished meanders (i.e., high sinuosity) and are in unconfined landscapes.
  • Red maple-tamarack peat swamp (guide)
    A swamp that occurs on organic soils (peat or muck) in poorly drained depressions. These swamps are often spring fed or enriched by seepage of mineral-rich groundwater resulting in a stable water table and continually saturated soil. The dominant trees are red maple and tamarack. These species usually form an open canopy (50 to 70% cover) with numerous small openings dominated by shrubs or sedges.
  • Rich graminoid fen (guide)
    A wetland of mostly grasses usually fed by water from highly calcareous springs or seepage. These waters have high concentrations of minerals and high pH values, generally from 6.0 to 7.8. Plant remains do not decompose rapidly and these grasses usually grow on older, undecomposed plant parts.
  • Rich hemlock-hardwood peat swamp (guide)
    A swamp that occurs in central New York in depressions or concave slopes which receive groundwater discharge. These swamps usually have a fairly open canopy (50 to 70% cover), scattered shrubs, and a diverse groundlayer with sedges, mosses, and forbs. The characteristic canopy trees are eastern hemlock (which usually have at least 20% cover), red maple, yellow birch, black ash, tamarack, white pine, smooth serviceberry, balsam fir, and northern white cedar.
  • Rich sloping fen (guide)
    A small, gently sloping wetland that occurs in a shallow depression on a slope composed of calcareous glacial deposits. Sloping fens are fed by small springs or groundwater seepage. Like other rich fens, their water sources have high concentrations of minerals and high pH values, generally from 6.0 to 7.8. They often have water flowing at the surface in small channels or rivulets.

* probable association but not confirmed.

Associated Species

  • Acer rubrum var. rubrum (common red maple)
  • Alnus incana ssp. rugosa (speckled alder)
  • Caltha palustris (marsh-marigold)
  • Carex leptalea (bristle-stalked sedge)
  • Carex stipata
  • Carpinus caroliniana
  • Cypripedium reginae (showy lady's-slipper)
  • Geum rivale (purple avens, water avens)
  • Glyceria melicaria (slender manna grass)
  • Glyceria striata (fowl manna grass)
  • Larix laricina (tamarack)
  • Leersia oryzoides (rice cut grass)
  • Lindera benzoin (spicebush)
  • Osmunda cinnamomea
  • Osmunda regalis
  • Poa palustris (fowl blue grass)
  • Poa trivialis
  • Rhamnus alnifolia (alder-leaved buckthorn)
  • Saxifraga pensylvanica
  • Sphagnum centrale
  • Sphagnum contortum
  • Sphagnum warnstorfii
  • Symplocarpus foetidus (skunk-cabbage)
  • Thelypteris palustris
  • Toxicodendron vernix (poison-sumac)
  • Tsuga canadensis (eastern hemlock)


New York State Distribution

Most of our populations are within or near the Cayuga Lake basin. There are a few scattered populations elsewhere ranging from Albany to the Black River Valley and the Lake Ontario lakeplain. This grass is easily overlooked and is likely present at more sites than currently reported. New York is at the northeastern edge of its range.

Global Distribution

This grass is found in widely scattered wetlands from New York, Pennsylvania, Virginia, and North Carolina west to Minnesota and Iowa.

Identification Comments

General Description

Poa paludigena is a very slender, weak-stemmed plant with an open inflorescence containing few flowers. It can be found as one plant or in small tufts that grow from one half to two feet tall. There are only 2-3 short slender leaves with boat-shaped tips. The branches in the inflorescence are mostly in groups of one or two or rarely three. Three veins are visible on the lemmas and these have small hairs along the base.

Identifying Characteristics

The culms of this grass are either solitary or in very small tufts; they are not rhizomatous. These slender and weak culms may reach 60 cm tall. The leaves are 0.25-3 mm broad, and there are usually only 2 or 3 stem leaves. The ligules are short, 0.5-1.5 mm long, and truncate. The panicle is 3-13 cm long and the branches are mostly in 1's or 2's. The glumes are about 2 mm long. The lemmas are 2.5-3.5 mm long, scarcely webbed at base, with marginal nerves. The keel is pilose at base. The intermediate nerves of the lemma are obscure and glabrous, thereby appearing 3-veined.

Best Life Stage for Proper Identification

Best life stage for ID: in fruit. Characteristics needed to ID: culms with leaves and mature achenes.

Similar Species

Poa sylvestris, Poa palustris, and Poa nemoralis are similar in appearance to Poa paludigena but they have more stem leaves and their inflorescence branches are in groups of 3-5.

Best Time to See

Mature fruits from this grass may be found from early until late summer. Surveys should be conducted only when mature fruits may be collected.

  • Fruiting

The time of year you would expect to find Slender Marsh Blue Grass fruiting in New York.

Slender Marsh Blue Grass Images


Slender Marsh Blue Grass
Poa paludigena Fern. & Wieg.

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Monocotyledoneae (Monocots)
        • Order Cyperales
          • Family Poaceae (Grass Family)

Additional Common Names

  • Bog Bluegrass
  • Marsh Bluegrass
  • Marsh Spear-grass

Additional Resources

Best Identification Reference

Hitchcock, A.S. 1951. Manual of the grasses of the United States. 2nd edition revised by Agnes Chase. [Reprinted, 1971, in 2 vols., by Dover Publications, Incorporated, New York.]

Other References

Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

Mitchell, Richard S. and Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. Contributions to a Flora of New York State. Checklist IV. Bulletin No. 490. New York State Museum. Albany, NY. 400 pp.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.

Rhoads, Ann F. and Timothy A. Block. 2000. The Plants of Pennsylvania, an Illustrated Manual. University of Pennsylvania Press, Philadelphia, PA.

Voss, E.G. 1972. Michigan Flora, Part I. Gymnosperms and Monocots. Cranbrook Institute of Science Bulletin 55 and the University of Michigan Herbarium. Ann Arbor. 488 pp.

Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research University of South Florida]. New York Flora Association, Albany, New York


About This Guide

Information for this guide was last updated on: January 15, 2009

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Poa paludigena. Available from: Accessed June 21, 2024.