A typically erect perennial with a naked stem 1-12 dm. high. The generally arrowhead-shaped leaves have great variability in width, which may be a response to varying water depths.
Male flowers have many stamens.
The flattened nutlets are packed into a dense head. Nutlets are 2.5-4 mm. The rhizomes end in an edible tuber. In flower during July and August. Broad-leaved arrowhead is a nonpersistent emergent found in shallow water and on saturated soils of marshes, shrub swamps, wooded swamps, open bogs, and stream and lake margins.