4. Heteranthera reniformis Ruíz & Pav. (mud plantain)

Map 767

Plants annual. Vegetative stems creeping, at least some of the leaves at well‑separated nodes. Leaves dimorphic, clustered, the rosette leaves of seedlings linear and lacking a well‑defined blade, the emergent or floating, later leaves long‑petiolate, the blades 1–4 cm long, often wider than long, kidney‑shaped to nearly circular, deeply cordate at the base, the tips broadly rounded or sometimes acute. Inflorescences produced on specialized flowering stems, these 1–9 cm long, erect to spreading. Inflorescences stalked spikes that are barely exserted or up to 2 times as long as the spathes. Perianth white, zygomorphic, the tube 5–10 mm long, the lobes linear to narrowly oblong, 3–6 mm long, the middle lower lobe the longest, descending, the 5 upper lobes clustered, erect to spreading, the middle upper one with 2 yellow or green spots. Stamens unequal, the filaments densely hairy with white hairs. 2n=48. Late May–September.

Widely scattered and uncommon in the state, mostly south of the Missouri River (Illinois to Nebraska, south to Oklahoma and Mississippi; disjunct in South America). Emergent aquatic, usually in shallow, stagnant or slow‑moving water or along muddy margins, in ponds, lakes, ditches, swamps, sloughs, and rice fields.