The oldest public wildflower garden in the United States
Common Dodder (Scaldweed, Swamp Dodder)
Cuscuta gronovii Willd. ex Roem & Schult
Convolvulaceae (Morning Glory)
Late Summer Flowering
Dodder is a parasitic herbaceous vine with yellow to orange smooth stems. There are a number of species of the genus, all parasitic. Several additional species are found in the Garden. Identification requires close attention to detail, but the generalities of the species are similar to the species described here.
Leaves usually do not exist except for scale-like remnants.
The flowers are 5-parted, white, about 1/8 inch long that appear in a dense cluster along the stem. The flowers are stalkless and the petals are ovate with tips that are rounded to obtuse, and appear to be wax-like. The lobes of the calyx are much shorter and yellowish-green. The ovary is large, rounded, with two prominent styles that have blunt tips. From the base of the petals rise 5 stamens with whitish filaments and anthers that turn brownish-yellow at maturity.
Seeds are held in the pea-like ovary capsule until the tip splits open to disperse them on the ground and when they germinate the slender thread-like stems begin to climb up adjoining plants. The stems then put out small vesicles that attach to the host plant. As soon as there are a sufficient number of attachments for Dodder to draw nourishment from the host plant, the root withers away and the parasite lives completely off the host. If a host is not found within a few days of germination the plant dies.
See Eloise Butler's notes at the page bottom.
Research: There are a large number of Dodder species, some restricted to very local areas such as C. odontolepis, the Santa Rita Mountain Dodder. Dodders are somewhat specific as to which host plants serve it best and some important scientific work has been done to support the claim that dodder is sensitive to certain plant odors, or pheromones, and that the plant responds to favorite odors. Entomologist Consuelo De Moraes at Pennsylvania State has shown the C. pentagona will move quickly to a tomato plant but avoid a wheat plant. Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University has published much on this including What a Plant Knows: A Field Guide to the Senses. Nevertheless, a single Dodder can attach itself to a number of plants in a given area, thereby causing great harm to specific plant communities.
Habitat: Common Dodder is found in moist areas from swamps to moist meadows and woods. It tolerates partial shade but the stems do not get as deep an orange color as when in full sun.
Names: Some botanical authorities put this plant in the older Dodder family - the Cuscutaceae. Based on the work of the Angiosperm Phylogeny Group, most dodders are assigned to the Morning Glory Family and Minnesota authorities are following that lead. The genus name Cuscuta is the Latin name for Dodder. The species, gronovii is an honorary for Johan Fredrik Gronovius (1690-1762) of Leyden, a naturalist, a supporter of Linnaeus and author of Flora Virginica published 1739-1743. Unfortunately, the material he used for the study was supplied to him by Virginia botanist John Clayton and he published using Clayton's material and notes without telling him or getting permission.
The author names for the plant classification are as follows: First to publish was ‘Willd.’ who was Carl Ludwig Willdenow (1765-1812), German botanist, a founder of the study of the geographic distribution of plants. He was director and curator of the Botanic Garden of Berlin. His work was amended by 'Roem & Schult.' who together published the 16th edition of Linnaeus’ Systema Vegetabilum. The names refer to Johann Jacob Roemer (1763-1819) Swiss botanist and Josef August Schultes (1773-1831), Austrian Botanist.
See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.
Above: Dodder climbing on a host plant. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: Dodder as commonly found entwining itself on a host plant.
Below: 1st photo - The 5-part white flowers have rounded tips on petals and appear to be made of wax. 2nd photo - Small vesicles reach out from the orange stem and attach to the host plant. The old rooting stem (to the right in the photo) then withers away and the Dodder lives off the host.
Below: Flower detail - The inside of the corolla has small fringed scales. The five stamens with their yellowish-brown anthers rise from the inside base of the petals. The large yellow-green ovary in the center has two styles with blunt tips.
Notes: Dodder is native to most of the U. S. and the southern Canadian Provinces except British Columbia, WA, CA, UT and NV. In Minnesota its range is the counties of the old deciduous forest belt running diagonally NW to SE with many exceptions. The majority of Minnesota Counties do not report it. There are nine known species found in Minnesota but three are known only from one county (Clay, Winona and Lake County). It is indigenous to the Garden area. Eloise Butler noted it in her Garden Log on Sept. 6, 1907.
Eloise Butler wrote of Dodder: "All the food of animals is directly or indirectly prepared from the elements of earth, water and air by green plants. Plants without leaf-green chlorophyll are, like ourselves, consumers instead of producers. Among them is the Dodder, an annual belonging to the Convolvulus family. The seed germinates in the ground. But as soon as the plantlet can stretch to neighboring vegetation the connection with the earth dies away and it twines closely around its hapless host, drawing out the life-sap with countless, tooth-like roots.
It is merely a yellow, leafless, thread-like stem, which in the course of time, will wreath its victim with a beautiful garland of compact, small white flowers. The dodder is pernicious in the garden and on the farm. A very inferior quality of flower or fruit, if any at all, would be produced by plants attacked by it. It is called love vine. A less demonstrative and less self-seeking affection is certainly to be preferred. We allow the Dodder to grow in the wild garden in order “to point a moral and adorn a tale,” but strive to keep it under restraint." Published July 30, 1911, Minneapolis Sunday Tribune. (Full article)
References and site links
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"