In his 1981 publication Rare Plants of New York State, Richard Mitchell regarded this plant as extirpated in New York since it had not been seen since 1925. Natural Heritage survey work by Bob Zaremba in the mid-1980s confirmed that this plant was still present at Hempstead, Long Island, and at seven more sites east to Montauk.
There are six existing populations, but additional surveys are needed to evaluate their current status. This species has not been widely targeted for surveys, so more populations should be found. There are 10 historical occurrences, but many of these are considered extirpated from western Long Island.
The short-term trend is unknown due to lack of recent surveys.
This species has probably remained stable over the long term, as new populations have been found to offset those that have been extirpated on western Long Island. It is thought that more populations will be found on eastern Long Island.
The biggest threat to this species is the succession of its woodland opening habitat to woody species that would convert the openings to forest and prevent germination. A seed bank can maintain the population for some time until disturbance returns however. Some populations also occur along trails, right-of-ways, or roads where the open habitat is maintained, but the plants are still threatened by direct disturbance such as displacement by exotic species, trampling, improper mowing, herbicide or bicycle use.
This species needs disturbance to reduce competition from woody plants and more aggressive herbaceous plants, but too much direct disturbance to the plants will reduce the population. Its habitat could be disturbed in the non-growing season to open it up for seed germination and colonization, but direct disturbance should be prevented during the growing season.
Some hybridization is known to exist with other Crocanthemum species on Nantucket and we should determine if this is happening on Long Island as well.
In New York, early frostweed is currently known to grow at a single location; a dry sandy slope along a powerline opening within a coastal oak-heath forest (New York Natural Heritage Program 2010). Dry, sandy soil (Gleason and Cronquist 1991). Dry, open sand and barrens (Fernald 1950).
This is currently only known from Nassau and Suffolk counties on Long Island.
Early frostweed is found along the Atlantic Coastal Plain from New Hampshire to North Carolina and inland from Pennsylvania south to Tennessee.
Early Frostweed is a low-growing (up to 30 cm) perennial herb species with stems up to 30 cm tall growing from a creeping rhizome. The leaves are alternate, the larger ones 1 to 3 cm long, and linear-spatulate to oblong linear in shape. It first bears a terminal cyme of 2 to 6 yellow flowers (often exceeded by later branches), and eventually closed cleistogamous flowers borne in the axils or tips of leafy branchlets. The fruit are capsules; those of open flowers are about 3 to 3.5 mm long and bear 12 to 15 seeds, while those of the cleistogamous flowers are 1.5 to 2mm long with 1 to 2 (3) seeds.
Flowers or fruit are necessary for identification.
There are four different Crocanthemum species in New York and these are often confused. Crocanthemum dumosum and H. canadense both have solitary flowers rather than the terminal clusters of C. bicknelii and C. propinquum. Crocanthemum bicknellii is the species most difficult to distinguish from C. propinquum. It differs from C. propinquum by tending to have taller (20 to 50 cm) branches, by having more (6 to 10) petaliferous flowers with the inner and outer sepals nearly equal (C. propinquum has outer sepals evidently shorter than the inner) and 12 to 26 seeds, and also by having cleistogamous flowers whose outer sepals have a free tip from 0.5 to 1 mm long (only 0.2 to 0.5 mm long in C. propinquum).
Crocanthemum dumosum flowers from mid-May into late June. Fruits may persist through mid-October.
The time of year you would expect to find Low Rock Rose flowering and fruiting in New York.
Low Rock Rose
Crocanthemum propinquum (Bickn.) Bickn.
Arrington and Kubitzki (2003) proposed reviving the segregate genus Crocanthemum for New World members of Helianthemum sensu lato based on morphology, nuclear and chloroplast DNA phylogenies, and geography. Their molecular work also shows that Hudsonia is nested within Crocanthemum but they did not address this in their classification and left Crocanthemum (excluding Hudsonia) as paraphyletic. Guzmán and Vargass (2009) molecular work also support a split of the old and new world taxa of Helianthemum sensu lato and again show Hudsonia nested within Crocanthemum. As a result, we tentatively support the segregation of new world taxa of Helianthemum to the genus Crocanthemum but expect further nomenclatural adjustments will need to occur once the Hudsonia-Crocanthemum clade is fully resolved. The four species of Crocanthemum that occur in New York are C. bicknellii, C. canadense, C. dumosum, and C. propinquum.
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.
Fernald, M.L. 1919. Helianthemum bicknellii and H. propinqum. Rhodora 21: 36-37. A19FER01PAUS.
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.
Hough, M.Y. 1983. New Jersey wild plants. Harmony Press, Harmony, NJ. 414 pp.
Mitchell, Richard S. 1986. A checklist of New York State plants. Bulletin No. 458. New York State Museum. 272 pp.
Mitchell, Richard S. and Charles J. Sheviak. 1981. Rare Plants of New York State. Bull No. 445. New York State Museum. Univ. of New York. State Ed. Department Albany, NY.
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. 2023. New York Natural Heritage Program Databases. Albany, NY.
Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the vascular flora of the Carolinas. Univ. North Carolina Press, Chapel Hill, NC. 1183 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
This guide was authored by: Stephen M. Young
Information for this guide was last updated on: September 6, 2012
Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Crocanthemum propinquum. Available from: https://guides.nynhp.org/early-frostweed/. Accessed May 29, 2023.