Culture
Easily grown in organically rich, moist to wet soils in full sun. Tolerates light shade, but full sun with good air circulation generally produces the best flowers, strongest stems, and the best environment for resisting potential diseases. Soils should never be allowed to dry out. Regular deep watering is advisable. Cut back stems to approximately 3-4 inches in late autumn. New growth shoots are slow to emerge in spring. Once new growth begins, however, it proceeds quite rapidly. Plants will benefit from regular fertilization during the growing season.
Noteworthy Characteristics
Hibiscus dasycalyx, commonly known as Neches River rose-mallow, is a rarely found perennial of the mallow family whose native territory is limited to three populations in seasonally inundated and regularly flooded bottomland areas near the Neches, Angelina and Trinity rivers in eastern Texas. Further declines in these native populations are currently threatened by a number of factors, primarily including habitat loss and genetic contamination of the species via interspecific hybridization which occurs as a result of encroachment in the wild by the closely related Hibiscus laevis (formerly H. militaris) and Hibiscus moscheutos, both of which grow in areas where Hibiscus dasycalyx occurs. H. laevis crosses easily with the within rare species, which makes it difficult to insure and maintain a pure genetic population.
Three additional populations have now been introduced and established in eastern Texas in order to expand growth and help protect the species from further decline or possible extinction in the wild.
Hibiscus dasycalyx was designated in September of 2013 by the U.S. Fish and Wildlife Service as a Threatened Species under the Endangered Species Act of 1973, as amended.
Neches River rose-mallow typically grows to 3-4’ (infrequently to 7’) tall and to 2-3’ wide. Bowl-shaped white flowers (3-6” wide) bloom singly from the leaf axils in the upper parts of the plant in summer (June to August) with that bloom sometimes extending into October in optimum growing conditions. Each flower features 5 overlapping, white (infrequently pink) petals, a dark reddish-purple center blotch and a prominent staminal column.
This plant is sometimes commonly called narrow-leaved hibiscus because it has the narrowest, deeply 3-lobed, finely-divided leaves of any plant in the genus. Leaves emerge red-purple in spring, but mature to medium/dark green. Rustic seedpods remain on the plant until November.
Alternate, broad-ovate to lanceolate leaves (3-8” long) with toothed margins are green above and white-hairy beneath. Leaves are lobeless or have 3-5 shallow lobes.
Genus name is the old Greek and Latin name for mallow.
Specific epithet is a combining form which comes from the Greek word dasys meaning dense or hairy in reference to the densely pubescent calyx and bracteoles on plant flowers plus the hairs on mature seeds.
Problems
No serious insect or disease problems. Susceptible to leaf spot, blights, rust and canker. Japanese beetles can severely damage plant foliage if left unchecked. Hibiscus sawfly, aphids, whiteflies, mealybugs and spider mites may appear.
Uses
Difficult to locate in commerce. Moist borders. Specimens. Useful in low spots or wet areas. Effective along streams or ponds. Temporary summer screen or hedge.