Vascular Plants of North Carolina
Account for Kidneyleaf Mud-plantain - Heteranthera reniformis   Ruíz & Pavónis
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Section 5 » Order Liliales » Family Pontederiaceae
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AuthorRuíz & Pavónis
DistributionWith the separation of H. multiflora from H. reniformis, all specimens of the latter must be identified anew. In NC, it appears that all, or nearly all, former records of H. "reniformis" actually belong to H. multiflora. For example, three specimens at NCU (University of North Carolina herbarium) from Davidson County are H. multiflora due to the short floral internode. On the other hand, there are so many specimens of "H. reniformis" in the various herbaria, and there are sightings or photos to back up some records, it is certain that at least the general range of the species can be summed up as "found primarily in the northeastern quarter of the state, including into the eastern edge of the Piedmont". Outer boundaries of the state range are certainly unknown, based on specimen confusion. Interestingly, if not oddly, Weakley's (2018) range map shows it as "uncommon" in the NC mountains, yet the SERNEC database lists no records for the mountains or the western Piedmont! However, Jim Matthews reported in late August 2020 two specimens at UNCC from Cabarrus and Mecklenburg counties--these had not been digitized.

This is a broadly Eastern species, ranging from CT, NY, and IL south to northern FL and TX. There are two clusters of records on the BONAP map, one being from southeastern NY in the Coastal Plain south to northeastern NC; and locally in the lower Mississippi River drainage.
AbundanceProbably rare to uncommon in the northern Coastal Plain, and very rare in the adjacent northeastern Piedmont, but as specimens may need to be re-examined, the abundance status is not well known. Status farther south or west is not clear, and thus the specimens from Carteret and Forsyth need to be re-examined, especially in light of Davidson County specimens being re-assigned by B. Sorrie from this species to H. multiflora. The NCNHP rightly considers this as a Watch List species.
HabitatThis species grows mainly in mud or very shallow water, in many situations. These spots can be on mudflats around lakes and ponds, on mudflats of tidal freshwater marshes, in swamp openings, in ditches, and in wet spots in trails or other clearings. Some of these muddy patches can be as small as one square-foot.
PhenologyBlooms from June into October. Fruits soon after blooming.
IdentificationThis species and H. multiflora are quite similar and can be confused. This species has mostly kidney-shaped leaves that are somewhat wider than long, as opposed to more rounded in H. multiflora. These thick and shiny leaves can be about 1-1.5 inches across. The short and often leaning or trailing flowering stem, often only a few inches long, contains mostly 2-8 flowers instead of 7-16 flowers in the other species. The flowers in H. reniformis are white to very pale blue, usually not as bright blue as some flowers in the other species. The anthers and filaments of this species contain white hairs; those in H. multiflora have dark purple hairs. There is also a difference in the internode below the spathe, which is longer in this species (more than 0.4-inch) than in H. multiflora. In general, this is a slightly smaller species, with white or whitish flowers, and more kidney-shaped leaves than found on H. multiflora. You stand a decent chance to find one or both species if you work often in muddy patches in the Albemarle Sound region or other areas in the northeastern Coastal Plain.
Taxonomic CommentsThis has always been a good species, but note that H. multiflora was not recognized as a species when RAB (1968) was published, and thus many if not most references in the 20th Century did not have H. multiflora pulled out of H. reniformis.

Other Common Name(s)Floating-leaf Mud-plantain
State RankS2? [S3?]
Global RankG5
State StatusW7
US Status
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