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| Hibiscus dasycalyx, The Necches River Rosemallow: a rare marsh plant known from only a few locations in eastern Texas |
Muenchhusia is a section of Hibiscus, composed of five closely related, hardy, perennial species native to North America. These species are mainly confined to marshy habitats in the eastern half of the United States, and are collectively identified as 'Rose-mallows'. The five species are: Hibiscus coccineus, Hibiscus dasycalyx, Hibiscus grandiflorus, Hibiscus laevis and Hibiscus moscheutos. Both H. lasiocarpos and H. palustris can be split from H. moscheutos but are sometimes ranked as subspecies.
Hibiscus dasycalyx, the Neches River Rosemallow, is a rare marsh plant known only from a few locations in eastern Texas. It is threatened by hybridization and encroachment of both Hibiscus laevis and Hibiscus moscheutos into its range, as well as loss of habitat along the Neches River and tributaries. Because Hibiscus dasycalyx hybridizes easily with both Hibiscus laevis and Hibiscus moscheutos, questions have been raised as to the taxonomic validity of Hibiscus dasycalyx. Two independent genetic studies (Mendoza 2004; Small 2004) indicate that it is in fact a distinct species, but more closely related to Hibiscus laevis than Hibiscus moscheutos. Robert Klips suggested that Hibiscus dasycalyx might best be regarded as a subspecies or variety of Hibiscus laevis (Klips 1995).
Hibiscus dasycalyx has delicate, slender, finely divided leaves on long, arching stems. The creamy white flowers are up to 15cm with dark burgundy eyes, and appear from June through August. Occasionally the petals will be pink. Plants often bloom into October depending upon water availability. This Hibiscus is distinguished from other native Hibiscus in that its flower has a densely pubescent calyx and its mature seeds are densely pubescent as well. Budding and leafing normally occur in late March and April, and seed pods are present from July through November. Seeds are buoyant in water for several hours thus aiding in the dispersal of the species.
The Neches River Rosemallow is a species of conservation concern with a history of declining numbers, and is a candidate for the federally listed Endangered Species Act. It is found naturally in only three confirmed counties of East Texas (Houston, Trinity, Cherokee and possibly Harrison) with one population recently discovered in the Davy Crockett National Forest in Houston County. It occurs naturally in wetlands, floodplains and in marsh conditions near the Neches, Trinity, and Angelina Rivers where the bases of the plants stand in water until late in the growing season (and may remain year round in marsh conditions). Like other Hibiscus in section Muenchhusia, the stems die back in late fall and resume growth from the rootstock in March to April. For best floral development, all of these American perennial mallows must be grown in full sun. While they are native to areas that are flooded during part of the growing season, they will often do well in cultivation with weekly watering.
