Cuscuta spp.

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Legend for Species Pages


Cuscuta spp.
  • Occurrence in Alberta – Native-Y, Exotic-N
  • AB Weed – entire genus elevated to Prohibited Noxious in some localities


C. gronovii Willd. ex Schult., a native species, is the only dodder known to occur in the wild in Alberta, according to ACIMS. It's NatureServe rank for Alberta is S1 (critically imperiled), elsewhere in Canada and the US it is secure. Alfalfa dodder, C. approximata Bab., and clover dodder, C. epithymum (L.) L., both exotics, do occur in the wild in adjoining jurisdictions and also threaten agriculture. C. gronovii is a threat to agriculture as well, but mainly on cranberries, whereas the exotics that might occur here can ruin alfalfa seed crops. Alfalfa dodder is parasitic mainly on clovers and alfalfa. Clover dodder attacks clover, alfalfa, and flax.

There are other North American native dodders that might occur here, all of which are less secure on a global basis than C. gronovii. Cuscuta gronovii Willd. ex Schult. var. gronovii, and Cuscuta cephalanthi Engelm. do occur here according to USDA Plants, but are not listed by ACIMS. Cuscuta coryli Engelm., Cuscuta indecora Choisy var. neuropetala (Engelm.) Hitchc., and Cuscuta megalocarpa Rydb. are known to have occurred in adjoining jurisdictions and are variously threatened or possibly extirpated. On the other hand Cuscuta pentagona Engelm., also a native, is apparently secure. It attacks at least 25 crops in 55 countries, including alfalfa, clover, fababean, beets, and carrots.

North American native species can be differentiated from exotic species by the capitate style. Styles of the exotic species are round or tapered, without any terminal enlargement.

Key to native Cuscuta species that might occur in Alberta (after Costea)

1A. Infrastaminal scales reduced to shallowly denticulate ridges, denticulate at the apex, bifid with 1–3 fimbriae on each side of the filament attachment or with shallowly toothed wings or lateral ridges. Cuscuta coryli.
1B. Infrastaminal scales well developed, fringed or fimbriate. 2.

2A. Calyx and corolla lobes have dissimilar apices: calyx lobes rounded, obtuse to subacute; corolla lobes acute, inflexed at apices. Cuscuta pentagona.
2B.Calyx and corolla lobes apices either acute, acuminate to long attenuate [rarely subacute], or obtuse to rounded; corolla lobes apex straight [inflexed only in Cuscuta indecora]. 3.

3A. Calyx and corolla lobes acute (rarely subacute), acuminate or longattenuate. Cuscuta indecora.
3B. Calyx and corolla lobes obtuse to rounded. 4.

4A. Flowers mostly 4-merous (rarely 3- or 5-merous). Cuscuta cephalanthi.
4B. Flowers 5-merous (rarely 3- or 4-merous). Cuscuta gronovii.

Expert ID assistance is most likely available from Dr. Mihai Costea at the Wilfrid Laurier University Herbarium who can identify most species from a few dried flowers or capsules sent by mail.


[1] Digital Atlas of Cuscuta, Photo Galleries


[2] M. Costea, Digital Atlas of Cuscuta (Convolvulaceae), Wilfrid Laurier University

C.W.O'Driscoll, Preliminary Review of the Genus Cuscuta in North America Prepared for the North American Plant Protection Organization PRA Panel, Canadian Food Inspection Agency, July / August 2003

Provisional Key to Cuscuta, for FNA, from Costea, M. 2007-onwards. Digital Atlas of Cuscuta (Convolvulaceae). Wilfrid Laurier University Herbarium, Ontario, Canada.

USDA, NRCS. 2012. The PLANTS Database (, 11 February 2012). National Plant Data Team, Greensboro, NC 27401-4901 USA.

Costea, M, Digital Atlas of Cuscuta (Convolvulaceae) Wilfrid Laurier University Herbarium, Ontario, Canada., accessed Feb 12 2012,

Costea, M, Nesom GL, Tardif FJ, Taxonomy of Cuscuta gronovii and Cuscuta umbrosa (Convolvulaceae) in North America. Sida 22: 197-207.

Costea, M, Tardif FJ, The biology of Canadian weeds. 133. Cuscuta campestris, C. gronovii, C. umbrosa, C. epithymum and C. epilinum.

NatureServe. 2011. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (Accessed: February 12, 2012 ).

Pages from Convolvulaceae Unlimited [web application] Updates can be located from this main page, using the search or index facilities provided.

  • [3] Costea, M., Cuscuta Genus Description, Oct 9, 2011</a>
  • [4] Costea, M., Cuscuta gronovii, Species Description, Oct. 11, 2011
  • [5] Costea, M. Cuscuta cephalanthi, Species Description, Sep. 30 2011
  • [6] Costea, M. Cuscuta pentagona Species Description, Oct. 9, 2011
  • [7] Er, Esmond, Cuscuta epithymum Species Description, Oct.31, 2011</a>
  • [8] Costea, M., Cuscuta coryli Species Description, Oct. 1, 2011
  • [9] Er, Esmond, Cuscuta approximata Species Description, Sep. 22, 2011