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.