Buttonbush Dodder
Cuscuta cephalanthi
Dodder family (Cuscutaceae)

Description: This herbaceous parasitic vine is a summer annual that is several feet along. It clings to adjacent vegetation using suckers (haustoria) on its stems. Lacking chlorophyll and a significant root system, this vine is dependent on its host plants for water and nutrients. The stems are usually pale yellow, sometimes becoming pale orange with age; they are glabrous and terete. Alternate leaves along the stems are reduced to tiny scales, or they are absent altogether. Small clusters of nearly sessile flowers occur at intervals along the stems. The peduncles and pedicels of these flowers are pale yellow to pale orange and glabrous. Each flower spans about 3 mm. (1/8" across), consisting of a white corolla with 4 lobes, a light green calyx with 4 lobes, 4 stamens, and an ovary with a pair of divergent styles. Less often, a flower may have a corolla with 5 lobes, a calyx with 5 lobes, and 5 stamens. The lobes of the corolla are deltate-ovate in shape and ascending to widely spreading. The calyx is glabrous with rounded lobes; it is shorter than the corolla. Both the corolla and calyx are short-tubular and bell-shaped (campanulate). At the base of the stamens within the corolla, are fringed scales that require at least a 10x hand lens to see. There are no floral bracts underneath the flowers. The blooming period occurs from mid-summer to early fall, lasting about 1½ months. There may be a mild floral fragrance. In the absence of insect pollinators, the flowers are self-fertile; they are replaced by globoid seed capsules spanning 3-5 mm. across. The glabrous seed capsules are surrounded by the withered remains of their corollas; they are initially light green, but turn brown at maturity. Each capsule is 2-celled, and each cell contains 2 seeds. The capsules eventually split open to release their seeds. The seeds are about 1.5 mm. long (or slightly more), ovoid in shape, and slightly compressed. There is a rudimentary root system at the seedling stage, but this is abandoned shortly after a suitable host plant has been found. If no host plant is found, the seedling dies within a few days.

Cultivation: This vine is typically found in wet to moist areas that are exposed to sun or partial sun. It cannot survive without a suitable host plant, although apparently many species of moisture-loving plants and shrubs can serve this purpose. Examples of suitable host plants include buttonbush (Cephalanthus occidentalis), water willow (Justicia americana), false nettle (Boehmeria cylindrica), asters (Aster spp.), goldenrods (Solidago spp.), bugleweed (Lycopus spp.), and even horsetails (Equisetum spp.). Soil type depends on the preferences of host plants, but can consist of sand, silt, loam, or muck. This vine can significantly weaken any host plant that it comes in contact with.

Range & Habitat:
The native Buttonbush Dodder is scattered throughout Illinois, where it is uncommon to occasional (see Distribution Map). Habitats include floodplain woodlands, swamps, soggy thickets along rivers, marshes, and wet prairies. This vine occurs in both sandy and non-sandy wetlands.

Faunal Associations: Robertson (1929) observed a small Halictid bee, Lasioglossum coriaceus, sucking nectar from the flowers of Buttonbush Dodder. Other small bees also visit the flowers for nectar, and possibly some moths (Müller, 1873/1883). According to Georgia (1913), the seeds of dodders can pass through the digestive tracts of grazing animals (e.g., cattle & horses) and remain viable. Thus, these animals may help to distribute these vines into new areas.

Photographic Location:
A sandy marsh at the Heron Boardwalk in Vermilion County, Illinois.

Comments: Buttonbush Dodder has a fairly typical appearance for the parasitic vines of this genus, although it is somewhat unusual in having 4-parted flowers (4-lobed corollas, 4-lobed calyces, and 4 stamens), rather than 5-parted flowers (5-lobed corollas, 5-lobed calyces, 5 stamens). Unlike other dodder species (Cuscuta spp.) with 4-parted flowers, the corolla lobes of Buttonbush Dodder usually spread outward rather than remain erect. Thus, it is a fairly easy species to identify during the blooming period. Some taxonomists have placed dodder species in the Morning Glory family (Convolvulaceae).