Habitats:
Ditches, marshes, mud, mudflats, riversides, swamps, wetland.
Fruit:
Oblong, dark brown or dark purple fruit, not flattened as in the similar looking Trifid Bur-marigold (Bidens tripartita). There are 2 to 4 hooked awns at one end of the fruit.
Leaves:
The broadly lance-shaped, toothed leaves are usually in opposite pairs going up the stem. Some of the upper leaves are alternate along the stems. Leaf blades measure up to 6 inches (15cm) long and 1.5 inches (4cm) wide. Smooth, green, purple-tinged, erect stems. Annual.