Cuscuta cephalanthi (Buttonbush Dodder)
|Also known as:
|Convolvulaceae (Morning Glory)
|part shade, sun; shores, swamps, moist fields, floodplains
|July - August
|3 to 4 foot vine
|Wetland Indicator Status:
|MN county distribution (click map to enlarge):
|National distribution (click map to enlarge):
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Small, tight clusters in short racemes or small panicles, the flower stalks (pedicels) and cluster stalks (peduncles) short and rather stout, the smaller clusters often proliferating and forming larger dense clusters around the stem. Flowers are 1/10 inch long or less, mostly with 4 (occasionally 5) rounded lobes much shorter than the floral tube and erect to spreading, often with the lobe tips curved in (inflexed) over the center. 2 styles with globular tips (capitate) and the 4(5) short, yellow-tipped stamens alternate between the lobes; stamens are attached to the petal near the base of the sinus between the petal lobes. The calyx is usually shorter than the floral tube and has 4(5) oval to egg-shaped lobes, rounded at their tip and overlapping at their base. The round central ovary is typically slightly depressed around the bases of the styles. 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, depressed (wider than tall) capsule about 1/8 inch diameter, initially green, brown when mature. The old dried up flower with stamens often persists as a cap on top of the mature capsule.
Buttonbush Dodder is one of nine Cuscuta species either present (6) or historically documented (3) in Minnesota. It is not too difficult to distinguish if you look for the mostly 4-lobed flowers, the lobes mostly erect, rounded to blunt tipped (not pointed), with the rounded-lobed calyx shorter than the floral tube, and the depressed, round fruit with persistent dried flower as a cap on top. Most dodders are associated with a broad host range, but 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. While both its common and Latin names imply Cuscuta cephalanthi hosts on Buttonbush (Cephalanthus occidentalis), it also flourishes on other species, both woody and herbaceous. Our images were taken on both Ontario aster and Sandbar Willow. While we could find no references made to this species as a pest, interestingly it is listed as conservation status "May be at Risk" throughout its native range in Canada.
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 by K. Chayka and Peter M. Dzuik taken at Kinnikinnick State Park in Pierce County, Wisconsin.
Have you seen this plant in Minnesota, or have any other comments about it?