Burweed Marsh Elder
Pollen Type: Weed
Cross-Reactivity: Other Marshelders, Poverty Weed
HS Allergy Extract: Marshelder/Poverty Mix (BPT)
Genus/Species: Cyclachaena xanthiifolia
Common Names: Marshelder, Giant Sumpweed, Rag Sumpweed, Carelessweed
Distribution: Central, West and Northeastern US.
Locations: Meadows, pastures, disturbed areas, roadsides, riverbanks, and saline marshes
Pollination Method: Wind-pollinated
Pollinating Period: June – October
Description: Burweed Marsh Elder is an herbaceous weed species in the sunflower family native to North American prairies. Over time, it has expanded its range to the west and east. This annual herb can grow 18″-72″ and features sturdy, upright, branching stems with fine ridges or grooves. The stems, which can be grayish-green, vertical, or climbing, are generally unbranched but may have straight, upright branches. They are hairless near the base and covered with fine, curved, or curled hairs above. Its leaves are opposite, becoming alternate towards the top of the plant. They are double-toothed, have rough hairs on the top, and are light green and fuzzy on the bottom. Lower leaves are long-stalked, while upper leaves are short-stalked and can grow to 2 3/4″. Its flowers appear in green to white 10″ panicled spikes, blooming from August-October. Some flowers are pistillate and fertile; others are perfect but sterile. Individual flower heads droop at the end of a 3/16″-1/4″ stalk. The whorl of bracts at the base of the flower head measures 1/16″-1/8″. The disk contains 8-20 male (staminate) florets in the center, with no more than ten usually present, and five female (pistillate) florets around the margin. The male florets’ stamens have filaments fused into a tube, and the anthers are free but closely arranged in a ring. The corolla, if present, is whitish and measures about 1/64″ long. The male (staminate) florets have a white to pale yellow corolla, about 1/16″ long. The fruit is an egg-shaped achene that is dark brown to nearly black and measures 1/16″ to 1/8″ long. It has a tuft of hairs attached to one end.