common mermaid-weed, more...
[Proserpinaca palustris var. amblyogona L.]
Etymology: Proserpinaca: Pliny's name of Polygonum meaning "pertaining to Proserpine"
Plants: perennial, semi-aquatic to aquatic, often found in clones; stems with many short, dark spikes
Leaves: alternate, submersed leaves oval to oblong and pinnately dissected
Flowers: purplish to greenish, 3-parted, small, sepals triangular; solitary to 3 together, stalkless in the axils of the emersed leaves
Fruits: 1/10" wide, nut-like, not winged, sides nearly flat, 3-seeded
Habitat: swamps, marshes, shores, ephemeral woodland ponds
Conservation Status: Native