- Scientific name: Gamochaeta purpurea
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Endangered (MA Endangered Species Act)
Description
Purple cudweed is an annual member of the aster family (Asteraceae) that colonizes open, disturbed habitats, growing to a height of 0.1-0.5 m (4-20 in). Both the stem and leaves of purple cudweed are coated with matted white hairs, giving the plant a woolly or cob-webbed appearance. The grayish-green stem is usually erect and unbranched, with a basal rosette and alternate leaves along the stem. Crowded clusters of white to brownish flowers form in the upper leaf axils, surrounded by pink or purple bracts.
The leaves of purple cudweed are distinctly bicolored, appearing woolly and white below, and grayish-green above, with the upper surfaces either hairless or sparsely covered in a cob-web of fine hairs. The leaves are spatulate or oblanceolate (tapering to the base), often with a sharp tip. The basal and lower leaves tend to wither before the flowers develop. The capitulescence (arrangement of the inflorescence) is usually continuous, and the receptacle is only shallowly concave. The outer involucral bracts are oval to triangular with pointed tips; the inner bracts are also pointed, and 3.5-5 mm (0.14-0.2 in) long. They appear purplish in bud, and whitish or silvery during fruiting.
In purple cudweed, the basal cells of hairs on the upper surface of the leaves are expanded and glassy, a diagnostic feature that distinguishes this plant from most similar species, which have hairs that are thin and thread-like to the base. The related Pennsylvania cudweed (G. pensylvanica) is also found in Massachusetts, but its leaves are only weakly bicolored, and obovate or spatulate, without pointed tips. The capitulescence of Pennsylvania cudweed is usually interrupted, with a deeply concave receptacle. Its inner involucral bracts are only 3-3.5 mm (0.12-0.14 in) long and are not pointed.
Life cycle and behavior
This is an annual species.
Population status
Purple cudweed is listed under the Massachusetts Endangered Species Act as Endangered. All listed species are protected from killing, collecting, possessing, or sale, and from activities that would destroy habitat and thus directly or indirectly cause mortality or disrupt critical behaviors. The Massachusetts Natural Heritage & Endangered Species Program has 13 records from 4 counties: Barnstable, Bristol, Dukes, and Nantucket. One of these records has been observed within the last 25 years.
Distribution and abundance
Purple cudweed has a highly restricted range in Massachusetts and is rare in many states in the Northeast. It is more common elsewhere, occurring across the eastern half of the United States and appearing, likely as a naturalized species, in the coastal and mountain West. It is found north into Ontario and British Columbia, and south into Mexico, Nicaragua, the West Indies, and South America. It has naturalized over much of the globe, including in Hawaii, New Zealand, Australia, and parts of East Africa.
Habitat
This species colonizes open, usually disturbed habitats, including roadsides, fields, woodland clearings and forest edges. It is found in Massachusetts in sandy habitats of the coastal plain, including pond shores, seasonally wet meadows, and sandplains.
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
The major threats to purple cudweed are invasive species, site shading, and trampling from recreational activities.
Conservation
Sites supporting purple cudweed should be monitored for invasions of exotic plants; if they are out-competing this species, a plan should be developed, in consultation with the MassWildlife’s Natural Heritage & Endangered Species Program (NHESP), to remove them. Known habitat locations should be protected from dramatic changes in light or moisture conditions. Locations that receive heavy recreational use should be carefully monitored for damage to purple cudweed or soil disturbance. If needed, trails should be re-routed to protect a population. All active management of state-listed plant populations (including invasive species removal) is subject to review under the Massachusetts Endangered Species Act and should be planned in close consultation with NHESP.
References
Flora of North America Editorial Committee, eds. 2008. Asteraceae. Flora of North America North of Mexico, Vols. 19-21. Oxford University Press, NY.
Haines, A. 2011. Flora Novae Angliae – a Manual for the Identification of Native and Naturalized Higher Vascular Plants of New England. New England Wildflower Society, Yale Univ. Press, New Haven, CT.
Nesom, G.L. 1990. Taxonomic status of Gamochaeta (Asteraceae: Inuleae) and the species of the United States. Phytologia 68: 186–198.
University of California, Integrated Pest Management. 2011. “purple cudweed.” http://www.ipm.ucdavis.edu/PMG/WEEDS/purple_cudweed.html
USDA SCS. 1991. Southern Wetland Flora: Field Office Guide to Plant Species. South National Technical Center, Fort Worth, TX.
Contact
| Date published: | April 29, 2025 |
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