Name: Cuscuta indecora Choisy
Family: Convolvulaceae, the Morning Glory Family
Common Names: Dodder, bigseed alfalfa dodder, bigseed dodder, largeseed dodder, pretty dodder, showy dodder (2,5,8,9).
Etymology: With Arabic origins, Kushkut, means dodder plant or parasitic plant; in New Latin, Cuscuta directly translates as dodder. The species name, indecora, means “non-ornamental” in Latin (3,16,17).
Botanical synonyms (1):
Cuscuta decora Choisy ex Engelm.
C. decora var. indecora Engelm.
C. hispidula (Engelm.) Engelm.
C. neuropetala var. minor Engelm. & A. Gray
C. parviflora var. vestita Progel
C. verrucosa var. hispidula Engelm.
Epithymum indecorum (Choisy) Nieuwl. & Lunell
Quick Notable Features (4):
¬ Yellow-orange stems, parasitic
¬ Small white flowers with 5 apically inflexed petals
¬ Capsules enclosed by remnant corolla
¬ Fringed, ovate scales subtend the stamens
Plant Height: The height of Cuscuta indecora depends on the host; H.L. Dean measured the length of a single plant of the genus Cuscuta at nearly half a mile (19).
Subspecies/varieties recognized (1):
C. indecora var. attenuata (Waterf.) Costea
C. indecora var. bifida Yunck.
C. indecora var. hispidula (Engelm.) Yunck.
C. indecora var. indecora
C. indecora var. integriuscula (Engelm.) Yunck.
C. indecora var. longiselapa Yunck.
C. indecora var. neuropetala (Engelm.) Hitchc.
C. indecora var. portoricensis Urb.
C. indecora var. subnuda (Engelm.) Yunck.
Most Likely Confused with: Cuscuta glomerata, C. cephalanthi, C. coryli, C. polygonorum, C. gronovii, and C. pentagona (2).
Habitat Preference: In Michigan, the species grows on Ambrosia artemisiifolia (2). C. indecora, as suggested by the common name bigseed alfalfa dodder, also parasitizes alfalfa crops (Medicago sativa), Asclepias sp., Artemisia sp. and other herbs and low shrubs (4,6,7). It thrives in moist pine forests, sandy openings, disturbed areas, along roads, and even in salty marshes (3,18).
Geographic Distribution in Michigan: C. indecora is found in Cass, Oceana, St. Clair, Wayne counties (2).
Known Elevational Distribution: The species was collected at 2750m in Tilcara, Argentina (1).
Complete Geographic Distribution: Native to North America, the species is found in these states of the U.S.: AL, AR, AZ, CA, CO, CT, FL, GA, IA, ID, IL, IN, KS, KY, LA, MD, MI, MN, MO, MS, MT, NC, ND, NE, NJ, NM, NV, OK, OR, SC, SD, TN, TX, UT, VA, WV, WY,PR, VI; it is also present in Canada (SK), Mexico, Belize, Cuba, Jamaica, Costa Rica, Ecuador, Venezuela, Colombia, Paraguay, Brazil, Argentina, and Morocco (1,5,9).
Parasitism: Parasitism is a type of symbiotic relationship in which one organism obtains nutrients directly from a host organism. This has a detrimental effect on the host, but benefits the parasite. Although parasitic plants are commonly known to lack chlorophyll, some species have green organs, making them partially photoautotrophic. The physical link between the parasite and the host is called a “haustorium,” and often occurs through xylem-to-xylem attachment. The host can vary, ranging from the mycorrhizae of trees, to grasses and hardwood trees. A parasite can maintain open or partially open stomata, allowing transpiration to aid in extracting nutrients from the host (14).
Vegetative Plant Description: As Cuscuta spp. germinate, they develop a short anchoring root, while a stem forms and nutates (rotates) in search of a host. When an attachment with a host has been created, the anchorage root dies (15). Additional means of finding a host have been suggested in the literature, such as positive photoautotrophy or growth toward a source of moisture or specific chemicals (10). The stems of C. indecora are fleshy, yellowish to light orange, filiform, and 0.4-0.7mm in diameter; they coil around the host plant in a dextral orientation. Leaves are absent, instead the plant bears very small scales that are ovate and erect (3,4,8,18).
Flower Description: The inflorescences are dense-panicled cymes bearing pedicellate, small, fragrant, fleshy, papillose white flowers (2-5mm long). The naked gamosepalous calyx is 5-parted, and shorter than the corolla; the lobes are ovate to lanceolate and apically acute. The corolla is campanulate and 5-lobed; the lobes are triangular, apically acute and inflexed, slightly shorter than the tube, and very finely serrate. The five epipetalous stamens can be faintly exerted or included, and bear a fringed scale at the base. The superior ovary is subglobose and 2-locular, the two distinct styles have an enlarged base, yellow or purple, and shorter than the ovary; the stigma is capitate (2,3,4,18).
Flowering Time: July-September (3,8).
Fruit Type and Description: The fruit is an indehiscent oblong to subglobose capsule bearing a persistent style, enclosed by the corolla. Each capsule bears 4 seeds (3,4).
Seed Description: In the genus Cuscuta, the defining characteristic of the mature embryo is the absence of cotyledons. This may be attributable to the fact that the first job of the young stem is to search for a host, not to photosynthesize. Each ovary bears four ovules, but one or more may abort, which causes variation in seed size and shape; a dodder seed may have zero, one, or two flat surfaces. C. indecora seeds are 1.2-2.1mm long and 1mm across (3,10,18).
Dispersal Syndrome: In unspecified members of the genus Cuscuta both germination in the capsule and seeds falling to the ground were observed, leaving water dispersal or other means a possibility for dispersal. Additionally, Cuscuta spp. seeds may be able to pass through the intestinal tract of a sheep and remain viable. Although this method of dispersal is unlikely, it extends the potential dispersal mechanisms to include zoochory (10).
Distinguished by: C. epithymum has a slender stigma, not capitate as in C. indecora, the style is longer than the ovary, and the circumscissile fruit is dehiscent, while that of C. indecora is indehiscent. C. glomerata has dense, sessile flowers subtended by bracts and free sepals, not pedicelled, bractless, and gamosepalous like C. indecora. C. cephalanthi, C. coryli, and C. polygonorum are 4-merous, C. indecora is 5-merous. The sepals of C. cephalanthi, C. gronovii, and C. polygonorum have rounded apices, not acute like in C. indecora. In C. coryli and C. polygonorum, the calyx is as long as or longer than the corolla, unlike in C. indecora. The calyx of C. pentagona is the same length as the corolla tube, and the corolla is not papillate (2).
Other members of the family in Michigan (number species): Calystegia (5), Convolvulus (1), Cuscuta (8), and Ipomoea (4) (source 2).
Ethnobotanical Uses: While no specific information has been located on species use of Cuscuta indecora, the following information unattributed to species is presented: “An Indian proverb states that the person finding the root of dodder will have access to all the riches of the earth” (10). This statement pertains to the wide use of Cuscuta spp. for medicinal purposes across Asia, from herbal mixtures to treat ovarian cancer and postmenopausal osteoporosis to antifungal and insecticidal applications (13). From another perspective, “The dodder’s rapid development and its stranglehold on and damage to the host have earned it a place in the superstition of many Western countries. The German “Teufelsxwirn” and Dutch “Duivelsnaaigaren” are vernacular names of this sort,” highlights Cuscuta’s standing as a noxious weed in many places (10).
Phylogenetic Information: Convolvulaceae joins four other families in the order Solanales (Montiniaceae, Sphenocleaceae, Hydroleaceae, and Solanaceae), which encompasses 165 genera and 4,080 species. The distribution of Convolvulaceae is extensive worldwide, excluding areas of extreme temperatures—the Sahara and Gobi Deserts, and areas of high latitude (Canada, Greenland, Russia, Antarctica, as well as the southern tip of South America). Convolvulaceae has been noted as the only Asterid I family whose seeds exhibit physical dormancy (10). Cuscuta spp., belonging to the subfamily Cuscutoideae, is the only genus within the family that is parasitic. Its placement in Convolvulaceae is openly debated, but is supported by similar flower morphology (10,11,12) as well as the twining habit.
Interesting Quotation or Other Interesting Factoid not inserted above: As much as 90% of alfalfa crops in the high deserts of southern California were infested with C. indecora in 1992 (6). Some sources place the genus Cuscuta in its own family, Cuscutaceae (5,8,9). Cuscuta indecora can parasitize more than one host at a time (18). Similar to other members of the genus Cuscuta, this species is considered a noxious weed in the United States (5).
Literature and websites used:
- Tropicos.org. Missouri Botanical Garden. 20 Nov 2012 http://www.tropicos.org/Name/8500687
- Michigan Flora Online. A.A. Reznicek, E.G. Voss, & B.S. Walters February 2011. University of Michigan. Web. November 20, 2012. http://michiganflora.net/species.aspx?id=856.
- Fernald, M.L. 1950. Gray’s Manual of Botany, 8th ed. New York: American Book Company.
- Britton, N.L. & H.A. Brown 1970. An Illustrated Flora of the Northern United States and Canada: Volume III. New York, NY: Dover Publications, Inc.
- USDA, NRCS. 2012. The PLANTS Database (http://plants.usda.gov/java/profile?symbol=PHPO2, 11/20/12). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- Cudney, D.W., S.N. Orloff, & J.S. Reints 1992. An integrated weed management procedure for the control of dodder (Cuscuta indecora) in alfalfa (Medicago sativa). Weed Technology 6(3): 603-606.
- Callizo, J., J. Ruygt, & G. Muth 1998. The Flora of Napa County, California: Cuscuta. Pacific Union College (online). http://www2.puc.edu/Faculty/Gilbert_Muth/Cuscuta.htm
- The Wildflower Center. 2011. Cuscuta indecora. Lady Bird Johnson Wildflower Center. http://www.wildflower.org/plants/result.php?id_plant=CUIN
- Gbif.org. Global Biodiversity Information Facility Website. Accessed: 20 November 2012.
- Kuijt, J. 1969. The Biology of Parasitic Flowering Plants. Los Angeles, CA, USA: University of California Press.
- Yuncker, T.G. 1920. Revision of the North American and West Indian species of Cuscuta. Illinois Botanical Monographs. 6(2&3):1-141.
- Olmstead, R.G. & S. Stefanović 2004. Testing the phylogenetic position of a parasitic plant (Cuscuta, Convolvulaceae, Asteridae): Bayesian inference and the parametric bootstrap on data drawn from three genomes. Systematic Biology 53(3): 384-399.
- Costea, M. & T.J. François 2005. The biology of Canadian weeds. 133. Cuscuta campestris Yuncker, C. gronovii Willd. ex Schult., C. umbrosa Beyr. ex Hook., C. epithymum (L.) L. and C. epilinum Weihe. Canadian Journal of Plant Science. 298.
- Clark, W.D., R. Moore, & K.R. Stern 1995. Botany. Dubuque, Iowa: Wm. C. Brown Publishers.
- Menninger, E.A. 1970. Flowering Vines of the World. New York, New York: Hearthside Press Incorporated.
- Brown, R.W. 1956. Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
- Stearn, W.T. 1972. Stearn’s Dictionary of Plant Names for Gardeners. New York, NY: Sterling Publishing Co. Inc.
- Marquardt, E.S. 2009. Foraging and host use of the parasitic plant Cuscuta indecora.Doctoral Thesis/Dissertation: University of Houston. http://gradworks.umi.com/33/71/3371162.html
- Dean, H.L. 1942. Total length of stem developed from a single seedling of Cuscuta. Proc. Iowa Acad. Sci. 49: 127–128.
Image Credits (all used with permission):
1) Image of whole plant courtesy of Mike Plagens – Nature Guide, http://www.arizonensis.org/sonoran/fieldguide/plantae/cuscuta_indecora.html
2) Image of inflorescence courtesy of Eve & George DeLange, http://www.delange.org/Dodder/Dodder.htm
3) Image of twining habit with flowers kindly provided with ©DCR-DNH, Gary P. Fleming
4) Image of twining habit with flowers kindly provided with ©DCR-DNH, Gary P. Fleming
5) Image of capsules courtesy of Eve & George DeLange, http://www.delange.org/Dodder/Dodder.htm
6) Image of seeds courtesy of Steve Hurst @ USDA-NRCS PLANTS Database, OK TO USE http://plants.usda.gov/java/largeImage?imageID=cuin_003_ahp.tif
7) Species distribution map, derived from the Michigan Flora Online.
Primary Authors: Cristine V. Santanna, John Bradtke, and Lauren Sopher with revisions and editing by Robyn J. Burnham.
© Robyn J. Burnham
For additional information on Michigan Plant Diversity species accounts, please contact Robyn J. Burnham via email: rburnham“at”umich.edu