Mud plantains have glossy, rounded or kidney-shaped leaves and purple to white flowers that have six petal lobes. One petal lobe points downward. The flowers all open in early to midmorning and close by midafternoon. They typically grow as emergent aquatic shoreline plants.
Missouri has four mud plantain species that are herbaceous annuals and look quite similar to each other.
Longleaf mud plantain (H. limosa) is distinguished from the others by its growth habit: unlike our other mud plantains, which have creeping stems with leaves arising from various nodes and are well-separated on the stems, its stalk is short, with the leaves seeming to arise together in a cluster. Also, its leaf blades are generally oval instead of kidney-shaped. Its purple to white flowers arise singly (not in clusters). The lower, middle petal lobe that points downward is slightly longer than the others. The top 3 petal lobes each have a yellow spot at their bases. Blooms June–October.
Roundleaf mud plantain (H. rotundifolia) has creeping stems. The leaf blades are lance-shaped to oval, mostly longer than wide. Its purple to white flowers arise singly (not in clusters). The top three petal lobes stand erect, pointing upward (the middle lobe has a yellow spot at its base); the middle lower petal lobe points straight downward and is the longest; and the other two petal lobes point out to either side, like outstretched arms. Blooms July–October.
Missouri mud plantain (H. missouriensis) (formerly called bouquet mud plantain, H. multiflora) has creeping stems. The leaf blades are kidney-shaped to nearly circular, often wider than long, with deeply heart-shaped bases. Its purple (rarely white) flowers arise in clusters of 3 or more flowers. In each flower, the lower petal lobe is longest and points downward, while the five upper petal lobes spread out as a cluster; the middle upper petal lobe has a darker purple area at the base containing 2 yellow spots. The stamens are densely hairy with purple hairs. Blooms July–October.
- In 2020, Charles N. Horn, a botanist who specializes in this genus, segregated the species formerly called H. multiflora into three different species, and the version that lives in Missouri is now called H. missouriensis. The species H. multiflora still exists, but it occurs only in southern South America. The other new segregate, H. pauciflora, lives in the Atlantic Coastal Plain and also doesn’t occur in Missouri. Botanists had long recognized the three as separate varieties; now they’re separate species.
Kidney-leaved mud plantain (H. reniformis) is most similar to Missouri mud plantain, with creeping stems and kidney-shaped to nearly circular leaf blades with heart-shaped bases. The petals are configured much the same, with the lower middle petal lobe longer and narrower than the other five. Unlike Missouri mud plantain, its petals are white, and the hairs on the stamens are white as well. The middle upper petal lobe has two yellow or green spots. In natural settings in Missouri, it has been collected only once. It may occur in cultivation in Missouri ponds, however. Blooms late May–September
Similar species:
Except for their much smaller flowers, mud plantains strongly resemble their invasive relative, water hyacinth (Eichhornia crassipes), one of the worst weeds in aquatic ecosystems. Water hyacinth is a nonnative invasive from tropical South America. It spreads so rapidly in canals and lakes that even boat travel becomes impossible. Missouri is at the northern edge of water hyacinth’s climatic tolerance, and it should never be released into natural waters. Water hyacinth has much larger purple flowers, and below its shiny, kidney-shaped leaf blades, the leaf stalks are inflated into swollen, air-filled pouches that enable the plant to float freely on the water’s surface.
In addition to the four mud plantain species described above, Missouri has a fifth native species in genus Heteranthera: water star-grass (H. dubia). There is definitely a family resemblance in the form of the flowers, but its flowers are yellow, and its leaves are very narrow. It is a perennial, common in the Ozarks and sporadic north of the Missouri River. It is not likely to be confused with the mud plantains above.
Pickerel weed (Pontederia cordata) is another member of this family. It is a well-known, large, emergent plant popular as a pond-edge ornamental. You won’t confuse it with any of the above.
Size varies. Plants start off small in spring, then they grow and spread into increasingly larger colonies as the season progresses.
All but one of Missouri’s mud plantain species are scattered in the Ozarks and along the Missouri River. Kidney-leaved mud plantain is known only from a single historical collection in New Madrid County. Any of them might be cultivated as pond plants statewide.
Habitat and Conservation
Mud plantains sprawl along the muddy edges and slow-moving or stagnant water of ponds, sloughs, ditches, creeks, and river bottoms. They usually grow as emergent aquatic plants on shorelines in shallow water, usually rooted in mud, but occasionally breaking free and floating in mats.
Status
All our mud plantains, except for kidney-leaved mud plantain, are scattered in the southern half of the state and along the Missouri River.
Kidney-leaved mud plantain, as a Missouri native, is known only from a single historical collection in New Madrid County. It may have been introduced to Missouri from elsewhere in its North American range, or it may be that the species was formerly more common here and the single collection represents a last survival of the species in Missouri. Missouri is on the edge of its current range. As a Missouri species of conservation concern, it falls into the interesting category of “unrankable.” This means that conservation biologists cannot determine how threatened this species might be, due to a lack of information or due to substantially conflicting information about status or trends.
Human Connections
Mud plantains are often used as attractive plants for pond shorelines or shallow water. People sometimes grow them in aquariums.
We often think of wildflowers as growing in grasslands, glades, roadsides, and woodlands, but aquatic plants can be delightful, too.
Ecosystem Connections
Emergent shoreline plants create valuable habitat for a wide variety of aquatic, amphibious, and water-loving land animals. Frogs and fish find important cover in the miniature thickets formed by the crowded plant stalks. Aquatic insects, snails, and other invertebrates explore and forage among the roots, stems, and under the leaves.
Plants whose roots penetrate the soil along shorelines play important roles in preventing erosion and holding streambanks in place.
The waterlily leafcutter (Elophila obliteralis) is one species whose caterpillars are known to eat mud plantain and other aquatic plants. It is a type of crambid moth. There are doubtless others that feed on these plants, as well.
The genus name, Heteranthera, means “different anthers” and refers to the fact that many members of the genus, including Missouri’s four mud plantains, have two different kinds of stamens. Each flower has three total stamens. Two of them are small, while one is larger. Mud plantain flowers do not produce nectar, so they reward their pollinators (usually certain types of bees) with pollen. But the plant needs to reserve some of its pollen for pollination! Apparently, certain anthers are specialized for feeding the pollinator, while other anthers are reserved for the pollen intended for cross-pollinating another flower. The anthers for rewarding the pollinators are usually bright yellow or some other eye-catching color, while those with pollen intended for pollination are colored the same as the rest of the flower (in this case, purple or white). The bee is attracted to the bright yellow pollen and snatches it up, while rubbing its body against the camouflaged purple anther, whose pollen will end up on the style of the next flower the bee visits.
