Long's Bittercress

Cardamine longii Fern.

Cardamine longii
Stephen M. Young

Dicotyledoneae (Dicots)
Brassicaceae (Mustard Family)
State Protection
Listed as Threatened by New York State: likely to become Endangered in the foreseeable future. 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
Not Applicable - A state conservation status rank is not applicable because the species is not a suitable target for conservation activities (e.g., species is a hybrid, a domesticated species, not native to New York, an accidental or infrequent visitor outside of its normal range, a transient or migrant just passing through the state, or a species with only unconfirmed or doubtful reports).
Global Conservation Status Rank
Vulnerable globally (most likely) - Conservation status is uncertain, but most likely at moderate risk of extinction due to rarity or other factors; typically 80 or fewer populations or locations in the world, few individuals, restricted range, few remaining acres (or miles of stream), and/or recent and widespread declines. More information is needed to assign a firm conservation status.


Did you know?

This plant is named for one of its discoverers, Bayard Long, a famous Pennsylvania botanist from the early 1900s. This is one of the few rare plants in New York where we have discovered more new populations than known historical populations. This may be due to the increased exploration in the last 20 years of the difficult terrain of freshwater tidal mud flats.

State Ranking Justification

This plant of tidal areas was once thought to be restricted to Long Island but in recent years has apparently been expanding its range northward up the Hudson River. Of the eleven known populations, nine are located along the Hudson River. The habitats on Long Island have been exploited, but most of today's known populations are found in protected landscapes. This inconspicuous plant is easily overlooked, so more populations are likely. Typical populations range from a few individuals to a few hundred plants.

Short-term Trends

More populations have recently been found along the Hudson River. Whether these have been here all along and only recently reported or if this plant has spread up the Hudson River is unclear. Since this is such an inconspicuous plant of tidal mud, there is a good probability they were simply overlooked for many years.

Long-term Trends

Similar to the short-term trend information, we can surmise that the long-term trend has at least been stable. There is a possibility this plant has spread northward and increased its numbers within New York, but documenting this positive trend will be difficult.

Conservation and Management


Habitat has been exploited on most of Long Island but the Hudson River occurrences seem to be secure.

Conservation Strategies and Management Practices

Monitor Phragmites invasion and erosion of river banks.

Research Needs

More research is needed to determine the best time to search for this plant. It seems that before late May and after mid-July it is very difficult to see this plant.



Mainly a plant of intertidal areas within tidal estuaries and backwater areas. These are often in shaded areas of tidal swamps, mudflats, and muddy banks along tidal creeks. A single non-tidal population is located on muddy, organic, alkaline soil within a swamp forest. (New York Natural Heritage Program 2004). Along tidal banks and muck-covered ledges shaded by northern white cedar (Thuja occidentalis) and yellow birch (Betula alleghaniensis) (Crow 1982). Tidal estuaries (Fernald 1970). Borders of salt marshes (Gleason & Cronquist 1991).

Associated Ecological Communities

  • Brackish intertidal mudflats (guide)
    A sparsely vegetated community, characterized by low-growing, rosette-leaved aquatics. The community occurs on exposed intertidal mudflats where water salinity ranges from 0.5 to 18.0 ppt. This community is best developed where mudflats are nearly level so that broad expanses are exposed at low tide. The rosette-leaved aquatics are completely submerged at high tide, and they are usually coated with mud.
  • Brackish intertidal shore
    A community of the intertidal gravelly or rocky shores of brackish tidal rivers and creeks where water salinity ranges from 0.5 to 18.0 ppt.
  • Brackish tidal marsh* (guide)
    A marsh community that occurs where water salinity ranges from 0.5 to 18.0 ppt, and water is less than 2 m (6 ft) deep at high tide. The vegetation in a brackish tidal marsh is dense and dominated by tall grass-like plants.
  • Dredge spoil wetland*
    A wetland in which the substrate consists of dredge spoils; reedgrass is a characteristic species.
  • Estuarine common reed marsh*
    A tidal marsh dominated by non-native reedgrass (Phragmites australis). Estuarine reedgrass marshes may become established in tidal freshwater, brackish, and salt marsh settings. Establishment usually follows alteration of the original marsh through impacts such as dredging, ditching, or impounding water.
  • Freshwater intertidal mudflats* (guide)
    A sparsely vegetated community characterized by low rosette-leaved aquatics. This community occurs on exposed intertidal mudflats where the water is fresh (salinity less than 0.5 ppt). This community is best developed where mudflats are nearly level so that broad expanses are exposed at low tide. The plants are completely submerged in 0.9 to 1.2 m (3 to 4 ft) of water at high tide and they are usually coated with mud.
  • Freshwater intertidal shore (guide)
    A community of the intertidal gravelly or rocky shores of freshwater tidal rivers and creeks, sometimes occurring at the base of cliffs. The vegetation may be very sparse.
  • Freshwater tidal creek (guide)
    The aquatic community of a shallow, tidally flooded freshwater creek with submerged areas averaging less than 2 m (6 ft) deep at low tide.
  • Freshwater tidal marsh (guide)
    A marsh community that occurs in shallow bays, shoals, and at the mouth of tributaries of large tidal river systems, where the water is usually fresh (salinity less than 0.5 ppt), and less than 2 m (6 ft) deep at high tide. Typically there are two zones in a freshwater tidal marsh: a low-elevation area dominated by short, broadleaf emergents bordering mudflats or open water, and a slightly higher-elevation area dominated by tall grass-like plants.
  • Freshwater tidal swamp (guide)
    A forested or shrub-dominated tidal wetland that occurs in lowlands along large river systems characterized by gentle slope gradients coupled with tidal influence over considerable distances. The swamp substrate is always wet and is subject to semidiurnal flooding by fresh tidal water (salinity less than 0.5 ppt).
  • Red maple-hardwood swamp (guide)
    A hardwood swamp that occurs in poorly drained depressions, usually on inorganic soils. Red maple is usually the most abundant canopy tree, but it can also be codominant with white, green, or black ash; white or slippery elm; yellow birch; and swamp white oak.
  • Saltwater tidal creek (guide)
    The aquatic community of a shallow, tidally flooded saltwater or brackish creek with submerged areas averaging less than 2 m (6 ft) deep at low tide.

* probable association but not confirmed.

Associated Species

  • Acer saccharinum (silver maple)
  • Acorus americanus (American sweet-flag)
  • Amaranthus cannabinus (salt marsh water-hemp)
  • Bidens bidentoides (estuary beggar-ticks)
  • Bidens cernua (nodding beggar-ticks)
  • Bidens laevis (smooth beggar-ticks)
  • Callitriche palustris (vernal water-starwort)
  • Crassula aquatica (pygmyweed)
  • Helenium autumnale (common sneezeweed)
  • Limosella australis (Atlantic mudwort)
  • Lindera benzoin (spicebush)
  • Lindernia dubia
  • Lythrum salicaria (purple loosestrife)
  • Nyssa sylvatica (black-gum, sour-gum)
  • Peltandra virginica (green arrow-arum, tuckahoe)
  • Pluchea odorata (salt marsh-fleabane)
  • Samolus valerandii
  • Typha angustifolia (narrow-leaved cat-tail)


New York State Distribution

A small plant limited to the estuaries of Long Island and the Hudson River.

Global Distribution

A plant of tidal estuaries along the Cathance River (Maine), Agawam River (Massachusetts), Saugatucket River (Rhode Island), Hudson River and Long Island (New York), and the Chesapeake Bay (Maryland and Virginia). Historical records known from New Hampshire, Connecticut, New Jersey, and Delaware.

Identification Comments

General Description

This is a small delicate mustard relative whose leaves and weak stems are often covered with mud from the tides. There are usually less than ten undivided leaves arranged alternately along the stem. They are rounded to kidney shaped. The small flower and fruit stalk arises from the top of the plant. The tiny flowers do not have petals and produce very narrow, oblong, thin, papery fruits about 5-10 mm long.

Identifying Characteristics

The leaves of this mustard relative are simple and reniform to suborbicular with a cordate base. Rarely there is a pair of rounded leaflets near the leaf base. The flowers are apetalous, 0.7-1.2 mm long, and subsessile. The siliques are lanceolate (5-10 mm long) and on thick pedicels (0.5-1.5 mm long).

Best Life Stage for Proper Identification

To properly identify this plant, one should have a mature plant with fruits and leaves.

Similar Species

C. pensylvanica is the other Cardamine species most similar and closely related to C. longii. Pennsylvania bittercress has larger fruits (1.7 to 2.7 cm ) than those of C. pensylvanica (0.5 to 1 cm). In addition C. pensylvanica stems have stiff hairs near its base (C. longii has a smooth stem), and obviously pinnate or pinnatifid leaves.

Best Time to See

This plant fruits from June through September, with some stalks occasionally persisting into October. Flowers are very small and often difficult to see, especially since they are often mud covered. Surveys should be conducted during the fruiting period.

  • Vegetative
  • Flowering
  • Fruiting

The time of year you would expect to find Long's Bittercress vegetative, flowering, and fruiting in New York.

Long's Bittercress Images


Long's Bittercress
Cardamine longii Fern.

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

Additional Common Names

  • Saltmarsh Bittercress

Comments on the Classification

The taxonomic status of this plant requires investigation. L.M. Eastman suggests that this may be just a growth form of Cardamine pensylvanica whose morphological expression is greatly influenced by tidal action (Crow 1982).

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

Crow, Garrett E. 1982. New England's Rare, Threatened, and Endangered Plants. Prepared for the United States Department of Interior, Fish and Wildlife Service, Northeast Region. June 1982.

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, New York State Department of Enviromental Conservation. March 1998. Element Occurrence Record Database. Latham, 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.

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


About This Guide

Information for this guide was last updated on: September 8, 2004

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Cardamine longii. Available from: https://guides.nynhp.org/longs-bittercress/. Accessed March 4, 2024.