Graham's Rock Cress

Boechera grahamii (Lehmann) Windham & Al-Shehbaz

Lawrence Gillett

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
Imperiled or Vulnerable in New York - Very vulnerable, or vulnerable, to disappearing from New York, due to rarity or other factors; typically 6 to 80 populations or locations in New York, few individuals, restricted range, few remaining acres (or miles of stream), and/or recent and widespread declines. More information is needed to assign either S2 or S3.
Global Conservation Status Rank
Secure globally - Common in the world; widespread and abundant (but may be rare in some parts of its range).


State Ranking Justification

There are 14 verified occurrences, several thousand plants.

Conservation and Management

Conservation Strategies and Management Practices




In New York, Purple Rock-cress has been collected primarily from open areas of calcareous rock, including marble cliffs, limestone woodlands, and calcareous pavement barrens, though elsewhere in its range it is not known as a calciphile (New York Natural Heritage Program 2011). Rocky slopes and sandy soil in prairies and open forests (FNA 2010). Sandy or gravelly clearings and borders of woods (especially aspen) and shores, rock outcrops and summits of "mountains." (Voss 1985). Sandy or rocky soil (Gleason and Cronquist 1991).

Associated Ecological Communities

  • Alvar pavement grassland (guide)
    This community consists of exposed, flat limestone or dolostone pavement with grassy or mossy patches interspersed throughout. Some examples may be solely grassland with no pavement.
  • Calcareous cliff community* (guide)
    A community that occurs on vertical exposures of resistant, calcareous bedrock (such as limestone or dolomite) or consolidated material; these cliffs often include ledges and small areas of talus.
  • Calcareous shoreline outcrop (guide)
    A community that occurs along the shores of lakes and streams on outcrops of calcareous rocks such as limestone and dolomite. The vegetation is sparse; most plants are rooted in rock crevices.
  • Limestone woodland (guide)
    A woodland that occurs on shallow soils over limestone bedrock in non-alvar settings, and usually includes numerous rock outcrops. There are usually several codominant trees, although one species may become dominant in any one stand.

* probable association but not confirmed.

Associated Species

  • Campanula rapunculoides (creeping bellflower)
  • Campanula rotundifolia (hare-bell)
  • Dryopteris marginalis (marginal wood fern)
  • Elymus hystrix
  • Geranium carolinianum var. sphaerospermum
  • Lonicera hirsuta (hairy honeysuckle)
  • Milium effusum
  • Ostrya virginiana (hop hornbeam, ironwood)
  • Packera paupercula (balsam groundsel)
  • Pellaea glabella
  • Poa compressa (flat-stemmed blue grass, Canada blue grass)
  • Polypodium virginianum (Virginian rock polypody, Virginian polypody)
  • Solidago arguta
  • Stellaria longipes
  • Thuidium abietinum
  • Thuja occidentalis (northern white cedar, arbor vitae)


New York State Distribution

Northern New York State, known from 3 topographic quads.

Identification Comments

Best Time to See

In New York flowering occurs from May to July, when the fruit begins to mature. The leaves persist as the fruit matures, into August. If found in July there may be both flowers and fruit present, facilitating identification.

  • Flowering
  • Fruiting

The time of year you would expect to find Graham's Rock Cress flowering and fruiting in New York.

Graham's Rock Cress Images


Graham's Rock Cress
Boechera grahamii (Lehmann) Windham & Al-Shehbaz

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

Additional Common Names

  • Purple Rock Cress


  • Arabis brachycarpa (Torrey & A. Gray) Britt.
  • Arabis x divaricarpa A. Nels. (pro sp.) [= Arabis drummondii x holboelii]
  • Boechera brachycarpa (Torr. & Gray) Dorn
  • Boechera divaricarpa (A. Nels.) A.& D. Löve

Comments on the Classification

Recognition of Boechera grahamii as the oldest vaild name for apomictic hybrids between B.stricta and B.collinsii (=Arabis holboellii var. collinsii in Rollins, 1993) resolves serveral longstanding nomenclature issues.

Additional Resources


Gandhi, K.N. 1999. Nomenclatural novelties for the Western Hemisphere plants. II. Harvard papers in Botany 4: 295-299.

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.

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

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

Windham, M.D., and I.A. Al-Shehbaz. 2007b. New and noteworthy species of Boechera (Brassicaceae) III: Additional sexual diploids and apomictic hybrids. Harvard Papers in Botany 12(1): 235-257.

Zaremba, Robert E. 1991. Corrections to phenology list of April 9, 1991.


About This Guide

Information for this guide was last updated on: August 10, 2011

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Boechera grahamii. Available from: Accessed May 26, 2024.