Alligator weed

Alternanthera philoxeroides

Stoloniferous, aquatic, semiaquatic or terrestrial perennial, glabrous; stolons to 10 m long, rooting at the nodes.

Leaves obovate to narrow-elliptic, 2–7 cm long, 10–20 mm wide, acute, sessile.

Inflorescence subglobose, 8–10 mm diam., of few to several flowers. Bracts ovate, acute to acuminate. Perianth segments elliptic, 4–4.5 mm long, acute, papery, white. Stamens 5. Style c. 0.5 mm long.