Summary

Did you know?

The leaves of mountain watercress can be eaten raw or cooked. They have a hot watercress-like flavor. Being that they are rare in New York, please don't eat our plants.

State Ranking Justification

Currently there are only five populations known with a total of less than 1000 plants. Only four additional historical locations have ever been recorded. Trends are stable and threats are low but it is expected that this plant will always be rare in the state.

Short-term Trends

Three of the five populations have been resurveyed with little change in the numbers or quality of plants.

Long-term Trends

The populations will probably remain stable for the foreseeable future since most of them are in areas where little change in the habitat is expected.

Conservation and Management

Threats

Most of the populations occur in areas where little change in habitat is expected.

Conservation Strategies and Management Practices

Since this species seems to prefer forested areas with springs and seeps an effort should be made to protect their hydrologic regime. Forested areas around the occurrences should remain intact.

Research Needs

The exact type of wetland system that this species prefers should be studied. This information could be used to help model its expected occurrence in the state.

Habitat

Habitat

A plant of sandy or muddy streamsides, beaver wetlands, spring seeps, and oxbows (New York Natural Heritage Program 2006). Springs, seeps, and stream edges (Rhoads and Block 2000). Wet soil, swamps, or running water (Gleason and Cronquist 1991). Springy places and brooksides (Fernald 1970).

Associated Ecological Communities

• Hemlock-northern hardwood forest (guide)
  A mixed forest that typically occurs on middle to lower slopes of ravines, on cool, mid-elevation slopes, and on moist, well-drained sites at the margins of swamps. Eastern hemlock is present and is often the most abundant tree in the forest.
• Intermittent stream* (guide)
  The community of a small, intermittent or ephemeral streambed in the uppermost segments of stream systems where water flows only during the spring or after a heavy rain and often remains longer, ponded in isolated pools. These streams typically have a moderate to steep gradient and hydric soils.
• Oxbow lake/pond (guide)
  The aquatic community of a small, shallow, usually stagnant lake or pond of fluvial origin that occurs in an old river meander or oxbow that has been cut off from an unconfined river or marsh headwater stream by deposition of a levee. Typically, the associated river periodically overflows this levee, restoring river water and biota to this lake type.
• Sedge meadow (guide)
  A wet meadow community that has organic soils (muck or fibrous peat). Soils are permanently saturated and seasonally flooded. The dominant herbs must be members of the sedge family, typically of the genus Carex.
• Shallow emergent marsh (guide)
  A marsh meadow community that occurs on soils that are permanently saturated and seasonally flooded. This marsh is better drained than a deep emergent marsh; water depths may range from 6 in to 3.3 ft (15 cm to 1 m) during flood stages, but the water level usually drops by mid to late summer and the soil is exposed during an average year.
• Shrub swamp (guide)
  An inland wetland dominated by tall shrubs that occurs along the shore of a lake or river, in a wet depression or valley not associated with lakes, or as a transition zone between a marsh, fen, or bog and a swamp or upland community. Shrub swamps are very common and quite variable.

* probable association but not confirmed.

Associated Species

• Acer rubrum var. rubrum (common red maple)
• Acer saccharum (sugar maple)
• Betula alleghaniensis (yellow birch)
• Cardamine pensylvanica (Pennsylvania bitter cress)
• Carex prasina (elegant drooping sedge)
• Carex scabrata (rough sedge)
• Carpinus caroliniana
• Chrysosplenium americanum (golden-carpet)
• Cornus racemosa (gray dogwood, red-panicled dogwood)
• Equisetum arvense (field horsetail, common horsetail)
• Erythronium americanum
• Gaultheria procumbens (wintergreen, teaberry)
• Glyceria canadensis (rattlesnake manna grass)
• Hydrocotyle americana (American marsh-pennywort)
• Impatiens capensis (spotted jewelweed, spotted touch-me-not)
• Iris versicolor (blue flag)
• Lycopus americanus (American bugleweed, American water-horehound)
• Maianthemum canadense (Canada mayflower)
• Mitella diphylla (two-leaved mitrewort, two-leaved bishop's-cap)
• Myosotis scorpioides (water forget-me-not)
• Onoclea sensibilis (sensitive fern)
• Ranunculus recurvatus
• Rorippa aquatica (lake water cress)
• Thalictrum thalictroides (rue-anemone)
• Tsuga canadensis (eastern hemlock)
• Typha latifolia (wide-leaved cat-tail)
• Uvularia sessilifolia (wild-oats, sessile-leaved bellwort)
• Veratrum viride (false hellebore, Indian corn lily)
• Viola sororia (common blue violet)

Range

New York State Distribution

Most of the New York populations are from the western Southern Tier, particularly in and around both the Allegheny Reservoir drainage and the Cattaragus Creek drainage. The historical record from Ontario County needs confirmation. Additional populations should be expected from the stream gorges that drain into Lake Erie as well other large river drainage systems in western New York.

Global Distribution

This mustard relative ranges from Georgia, north through the Appalachians to New York.

Identification Comments

General Description

Mountain watercress is a small, semiaquatic perennial with short trailing stems that sometimes produce runners that root at the nodes. The leaf blades are round to heart-shaped with unevenly wavy edges. The leaf stalks are about as long as the leaves and they often have one or two small lateral lobes below the main leaf blade, especially on the larger leaves. The flowers have four white petals about 1/8 to 1/4" long. The fruiting stalks are about 3/4" long and stick out from the stem. The light tan fruits are very narrow, about 3/4" long and usually infertile.

Identifying Characteristics

This low growing plant has stems that are weak or decumbent with trailing branches. The roots are fibrous. The leaves are simple, all are mostly alike, roundish to somewhat angled, and often cordate at the base. The flower petals are 5-10 mm long.

Best Life Stage for Proper Identification

For proper identification, plants should have flowers or be in fruit. To verify the identity, collect a voucher specimen.

Best Time to See

This plant flowers May through June and fruits persist until early fruit. Surveys should be conducted during the flowering and fruiting period, which fortunately means surveys can be conducted pretty much any time during the growing season.

Round-leaved Water Cress Images

Cardamine rotundifolia
Troy Weldy

Cardamine rotundifolia
Troy Weldy

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Taxonomy

Round-leaved Water Cress
Cardamine rotundifolia Michx.

• Kingdom Plantae
  • Phylum Anthophyta
    • Class Dicotyledoneae (Dicots)
      • Order Capparales
        • Family Brassicaceae (Mustard Family)

Additional Common Names

• Mountain Watercress
• Roundleaf Watercress

Comments on the Classification

The taxonomy of this species may be questioned. It may simply represent a more aquatic form of a more common Cardamine species.

Additional Resources

Best Identification Reference

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.

Other References

Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 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. 2023. New York Natural Heritage Program Databases. Albany, NY.

Newcomb, Lawrence. 1977. Newcomb's Wildflower Guide: An Ingenious New Key System for Quick, Positive Field Identification of the Wildflowers, Flowering Shrubs, and Vines of Northeastern and North-Central North America. Little, Brown and Company. Boston.

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

Rollins, R.C. 1993a. The Cruciferae of continental North America: Systematics of the mustard family from the Arctic to Panama. Stanford Univ. Press, Stanford, California. 976 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 http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York

Weldy, Troy W. and David Werier. 2005. 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, NY. Available on the web at (http://newyork.plantatlas.usf.edu/).

Links

• Google Images
• NatureServer Explorer
• USDA Plants Database

About This Guide

This guide was authored by: Stephen M. Young

Information for this guide was last updated on: August 11, 2017

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Cardamine rotundifolia. Available from: https://guides.nynhp.org/mountain-watercress/. Accessed December 5, 2023.