Cuscuta glomerata (Rope Dodder)
|Also known as:||Aster Dodder|
|Family:||Convolvulaceae (Morning Glory)|
|Habitat:||part shade, sun; moist soil; prairies, sedge meadows, swamps|
|Bloom season:||July - September|
|Plant height:||3 to 4 foot vine|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Dense rope-like coil of stalkless white flowers spiralling up the main stem of its host. Flowers are 1/8 inch long, with 5 fused petals, the lobes narrow lance-like, pointed at the tip, and spreading star-like to slightly curled back (reflexed). The 5 calyx lobes are long and narrowly triangular, as long as the floral tube, loose with tips reflexed; around the base of the calyx are 8 to 15, spreading to ascending, triangular bracts. In the center of the floral tube is the ovary with two elongated styles, each about as long as the ovary with a prominent round stigma at the tip (capitate); the ovary is swollen around the base of the styles creating a small ridge called a stylopodium. 5 yellow-tipped stamens extend out of the tube, and are attached to the petal below the base of the sinus between the petal lobes. Hidden inside the floral tube, surrounding the ovary, are fringed scales that barely reach the base of the stamens, typically shorter.
Leaves and stems:
Leaves are tiny and scale-like or absent altogether. Stems are hairless and slender, typically yellow to orange, forming wiry masses that twist around and are supported by the host plant. Along the stem are small appendages (haustoria), modified roots that penetrate the host plant and draw moisture and nutrients from it.
Fruit is a round but flattened (wider than tall) capsule, about 1/8 inch diameter, the dried stylopodium creating a thickened ridge around the opening at the tip of the capsule, from which the seeds are disseminated. Capsules are brown when mature.
Rope Dodder is one of nine Cuscuta species either present (6) or historically documented (3) in Minnesota. This is perhaps the mostly easily identifiable of all our native dodders by its dense, continuous rope-like mass of flowers, as well as the dense bracts around the base of each flower. While most dodders are associated with a broad host range, some are fairly specialized to only a few species and when those species are natives in a dwindling habitat, some of those dodder species can become rare. This is listed as a Special Concern species in Wisconsin. Cuscuta glomerata is noted as having a preference for members of the Aster family, often on Goldenrod, though some specimens found in the location where these images were taken were hosting on Virginia Mountain Mint. As to the pest potential of Rope Dodder, there is little to no reference to it as such in literature.
All dodders are obligate parasites, that is they must obtain all their life support from a host species to grow and reproduce. Dodders not only sap energy from their hosts but are also capable of moving diseases from one host to another. When a dodder seedling germinates, it must quickly contact a suitable host upon which it immediately begins to twine around the host plant's stem, invading its tissue via the haustoria, after which the initial seedling root quickly withers away. As the stems grow, they contact and invade more stems, even crossing over and connecting to other suitable host species. All species of dodder are on the federal noxious weed list, except some native species (including Minnesota's natives) as well as a few, now widespread non-native species. Still all dodders, including natives, are "regulated" requiring federal permits for importation or transportation of seed.
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Photos courtesy Brian O'Brien taken at Cedar Mountain SNA, Redwood County.
Have you seen this plant in Minnesota, or have any other comments about it?
on: 2015-11-10 07:36:18
Very nice photos and description. It would have been great if you had photographed rope dodder flowering on Virginia mountain mint. It would have been the only documentation in the literature (that I have seen) of the plant flowering on Lamiaceae.
on: 2015-11-10 11:09:30
If only we could find it hosting on mountain mint (or any other species)! The images here were taken by someone else, who was lucky enough to stumble across it on one of his hikes in western MN.
on: 2017-07-31 17:33:11
We've been trying to eradicate new stands of Rope Dodder(?) for several years in our prairie. It grows and spreads very fast hosted on goldenrod.
on: 2017-09-27 23:01:05
If it's really rope dodder you should encourage it. It's probably quite a bit rarer than any of your goldenrods.
on: 2018-09-24 19:31:21
Rope dodder was prolific in a relatively small area of the calcareous fen at Ottawa WMA on September 11 when I visited there with friends. In response to the comment from John above, I do have photos of rope dodder hosting on mountain mint.
on: 2018-12-03 10:03:41
Noted quite a bit of dodder off the Louisburg Grade in Section 20, Township 120 North, Range 44 West, NWNE in December 2017. Growing mostly on sunflowers. Keyed out to native dodder by Iowa State. Area was burned the previous spring. McCormac & Windus noted in 1993 that it seemed to grow better after an area is burned.
on: 2020-07-18 22:24:16
Observed today on Helianthus, in wet prairie on south side of the Minnesota River within Big Stone National Wildlife Refuge.
on: 2021-09-06 07:15:30
There is a small colony on the North East side of the Quarry Hill Park savanna (rochester city park). Easily seen from the trail.
on: 2021-09-29 11:04:56
It was quite abundant on the Osmonson Tract on Lac qui Parle WMA in the spring/summer of 2021. This area had a prescribed burn on it on April 29th and it showed up in abundance after the fire. It was also observed in the spring of 2018 on the Thompson Tract as well after a prescribed burn occurred the previous spring. All dodder observed was associated with species of wild sunflower.
on: 2022-07-31 00:20:54
Saw on our hike today on the savanna part of the trail. Just a small patch of it growing around the purple cone flowers. Absolutely fascinating! Never seen before.