Cuscuta polygonorum is a parasitic annual herb, orange-stemmed vine, closely entwining host plant and entering host by numerous haustoria; vines strongly phototrophic, climbing only upward and counterclockwise, forming tangled masses at top of host stem, seedling root system degenerates when haustorial connection to host formed.
Leaves none or scale-like, alternate.
Flowers white, 4-parted, 0.2 cm, petal lobes triangular, tips pointed, calyx lobes as long or longer than petal tube, tips very blunt; inflorescences of small, dense clusters.
Fruit dry, hollow capsule, whitish, rounded, cupped by withered flower parts, 0.2 x 0.3 cm, persistent into winter, massed at tops of host stems; seeds 2-4, about 0.1 cm.
Wetland status: NL.
Frequency in NYC: Rare (NYS S1, E).
Habitat: In open areas on other herbs, occasionally on shrubs.
Notes: May kill host. Listed as a noxious weed by the USDA (USDA 2004).