Smartweed Dodder

Cuscuta polygonorum Engelm.

USDA Plants website

Dicotyledoneae (Dicots)
Convolvulaceae (Morning-Glory Family)
State Protection
Listed as Endangered by New York State: in imminent danger of extirpation in New York. 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
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
Secure globally - Common in the world; widespread and abundant (but may be rare in some parts of its range).


Did you know?

The first collections were from Long Island with the earliest known from 1896. The common name may come from a Middle Dutch word meaning the yoke of an egg referring to the yellow color of some of the flowers of Cuscuta. Dodder is an annual but some of its connections to the host plant (haustoria) may survive the winter and start new plants already on the host in the spring. The vines always seem to wrap around the host plant in a counterclockwise direction. Dodder is a speed demon when it comes to finding a host. Germination, emergence and attachment to the host may occur in as little as 24 hours and the seedling must find a host in 5-10 days or it will die (Wikipedia contributors).

State Ranking Justification

There are three existing populations but the total size of each population is unknown. In addition, three old reports of plant locations remain unconfirmed and two locations have been extirpated. Two additional locations known from 1949 and 1967 respectively, have not been resurveyed.

Short-term Trends

Short-term trends are unknown due to the lack of revisits to all of the known populations.

Long-term Trends

This plant has always been very rare in New York and long-term trends remain stable. Not all of the old records have been resurveyed but two are now considered extirpated while two new locations have been found.

Conservation and Management


No threats are known at this time but since the populations are in heavily-used parks there may be threats from direct human disturbance and invasive species.

Conservation Strategies and Management Practices

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 or eliminate the population. Its habitat could be disturbed in the non-growing season, by mowing, brush cutting or prescribed fire for example, to open it up for seed germination and colonization but direct disturbance should be avoided during the growing season.

Research Needs

Research is needed into the life history of this plant to see if it can be surveyed every year and how populations move around and change size. Host plant preferences should also be studied.



The few New York collections have been from cattail marshes and wet meadows, with the Cuscuta polygonorum growing on Typha or Polygonum species (New York Natural Heritage Program 2010). Moist shores and riverbanks, parasitic on Polygonum and other hosts (Rhoads and Block 2000). Low ground, on Polygonum, Lycopus, Penthorum and other herbs (Fernald 1970).

Associated Ecological Communities

  • Cobble shore wet meadow* (guide)
    A community that occurs on the cobble shores of lakes and streams where the substrate is moist from seepage or intermittent flooding. These communities are likely to be scoured by floods or winter ice floes, but there is apparently no significant accumulation of pack ice.
  • Common reed marsh*
    A marsh that has been disturbed by draining, filling, road salts, etc. in which common reed (Phragmites australis) has become dominant.
  • Deep emergent marsh (guide)
    A marsh community flooded by waters that are not subject to violent wave action. Water depths can range from 6 in to 6.6 ft (15 cm to 2 m). Water levels may fluctuate seasonally, but the substrate is rarely dry, and there is usually standing water in the fall.
  • Impounded marsh*
    A marsh (with less than 50% cover of trees) in which the water levels have been artificially manipulated or modified, often for the purpose of improving waterfowl habitat.
  • 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.

* probable association but not confirmed.

Associated Species

  • Polygonum
  • Typha


New York State Distribution

This species is known from Queens to Suffolk counties on Long Island. It is also currently known from one location in Niagara County. There are unconfirmed reports from Ulster County in the 1960s, Dutchess County in 1985 and Monroe County in 1986.

Global Distribution

This parasitic plant is most common in the Midwest from Ohio west to Arkansas and Oklahoma, and north to North Dakota. There are scattered populations from eastern Texas northeast through Kentucky, Virginia, and Maryland to Pennsylvania, southeastern New York and Massachusetts.

Identification Comments

General Description

Dodders are parasitic, annual plants, the seedlings attaching to a host plant soon after they sprout. The mature plants lack chlorophyll, roots, or leaves. They consist only of the pale yellow or orangish stems, attached to the host plant via numerous haustoria (suckers), and the compact (2 mm) flowers. With prolific individuals, the overall appearance is of a tangled mass of bumpy orange string sprawled and twining over the host plant. Upon closer inspection, Smartweed Dodder has nearly sessile, white, 4-parted flowers which form dense clusters. The sepals are united at the base and triangular with acute, erect or ascending tips. The fruits are commonly wider (3 mm) than they are high and cupped at the base by the persistent corolla (Gleason and Cronquist 1991).

Best Life Stage for Proper Identification

This species is best identified when in flower.

Similar Species

Cuscuta cephalanthi and C. coryli are the other two New York dodder species with flower parts in fours. C. cephalanthii has rounded corolla lobes, and C. coryli has acute but papillate lobes with the tips inflexed. Cuscuta polygonorum has smooth, acute corollas with the tips erect or ascending (Rhoads and Block 2000, Gleason and Cronquist 1991).

Best Time to See

The best time to identify this plant is September when it has both flower and fruit characters.

  • Flowering
  • Fruiting

The time of year you would expect to find Smartweed Dodder flowering and fruiting in New York.

Smartweed Dodder Images


Smartweed Dodder
Cuscuta polygonorum Engelm.

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Dicotyledoneae (Dicots)
        • Order Solanales
          • Family Convolvulaceae (Morning-Glory Family)

Additional Resources


Costea, Mihai, Guy Nesom and Sasa Stefanovic. 2006. Taxonomy of the Cuscuta pentagona complex (Convolvulaceae) in North America. SIDA 22 (1): 151-175.

Fernald, M. L. 1950. Gray's manual of botany. 8th edition. Corrected printing (1970). D. Van Nostrand Company, New York. 1632 pp.

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. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

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

Yuncker, T.G. 1965. Cuscuta. In W.R. Buck, [ed.], North American Flora, series II, vol 4, 1-51. New York Botanical Garden Press, Bronx, New York.

Yuncker, Truman G. 1932. The Genus Cuscuta. Memoirs of the Torrey Botanical Club. Vol. 18(2). 113-331.


About This Guide

This guide was authored by: Stephen M. Young

Information for this guide was last updated on: September 20, 2012

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Cuscuta polygonorum. Available from: Accessed April 16, 2024.