Michaux's Sumac

Rhus michauxii

Description

Michaux's sumac, Rhus michauxii, or false poison sumac, is a densely hairy shrub with erect stems which are 1-3 ft (30.5-91.4 cm) in height. The shrub's compound leaves are narrowly winged at their base, dull on their tops, and veiny and slightly hairy on their bottoms. Each leaf is finely toothed on its edges. Flowers are greenish yellow to white and are four to five parted. Each plant is unisexual. With a male plant the flowers and fruits are solitary, with a female plant all flowers are grouped in three-to five-stalked clusters. The plant flowers from April to June. The fruit, a dull red drupe, is produced in October and November.

Habitat

Michaux's sumac grows in sandy or rocky open woods. Apparently, this plant survives best in areas where some form of disturbance has provided an open area. Eleven of the plant's 16 remaining populations are on highway rights-of-way, roadsides, or on the edges of artificially maintained clearings. Two other populations are in areas with periodic fires, and two more populations exist on sites undergoing natural succession. One population is situated in a natural opening on the rim of a Carolina bay.

Distribution

Until recently, surviving populations of Michaux's sumac were known only from North Carolina and one site in Georgia. Not even historical records existed for this plant in Virginia. But a recent discovery at Fort Pickett, an army base in Virginia, located what is now the species' largest known population, containing over 21,000 plants. Of the 15 existing populations in North Carolina, nine have less than 100 plants each, and three of these have less than one dozen plants each.

Threats

Perhaps the most crucial factor endangering this species is its low reproductive capacity. Only two of the plant's 16 remaining populations have both male and female plants. The apparent low genetic variability of the species, caused by geographic isolation, complicates this situation. Because of the clonal nature of this species and the scarcity of populations containing both male and female plants, the remaining populations may actually consist of only about two dozen genetic individuals. Hybridization of this plant with smooth sumac (R. copallina) and dwarf sumac (R. glabra ) is another threat to the plant's genetic integrity. In at least two historic sites of Michaux's sumac, hybrid plants (apparently crosses between R. glabra and R. michauxii ) have been found.

Michaux's sumac is threatened by the conversion of native habitat for agriculture and forestry, residential and commercial development, and the suppression of wildfires. Intolerant of shade, the plant can be overtaken by vegetative succession. It prefers open habitat maintained by fire or mowing. Several populations are along roadsides, where they are vulnerable to highway widening and herbicide application. Two of the plant's historic populations were destroyed by development—one by the construction of a water tower, and one by the conversion of the site to a pine plantation.Conservation and RecoveryThe plant is shade-intolerant, and some form of disturbance such as burning is necessary to control the growth of woody species around its habitat.Timber harvesting and road construction or maintenance should be carefully conducted to preserve this plant's habitat. Prescribed burning is being conducted at the North Carolina Sandhills Game Lands which has the largest population (137 plants).

Genetic analysis work is being done through a cooperative effort between the University of Georgia, the North Carolina Nature Conservancy, and the U.S. Fish and Wildlife Service's Asheville, North Carolina, Field Office. Researchers from the University of Georgia analyze tissue samples collected from the remaining North Carolina and Georgia populations for their genotypes. If possible, male or female plants may be reintroduced into unisex populations of compatible genotypes. The first reintroduction attempt, conducted in Georgia in cooperation with the Georgia Heritage Inventory and Woodlanders, a commercial nursery specializing in native plants, is doing well with good survival of transplanted material.

As part of the recovery effort for Michaux's sumac, the North Carolina office of The Nature Conservancy collected leaf tissue for genetic analysis and demographic data from the 21 locations of this endangered plant that remain in the sandhills and coastal plains of North Carolina and Georgia. The results of this research will be used to plan the rein-troduction of Michaux's sumac into its former range and to complement single-sex populations of the deciduous, rhizomatous shrub. Populations are extremely small, and most are made up of only one sex. When the species was listed in 1989, only seven of the then-known 16 populations were comprised of 100 or more plants, and only two included representatives of both sexes.

Very few of the previously known populations produce fruit. In contrast, the Fort Pickett population is prolific. The army is taking advantage of the situation by promoting the recovery of Michaux's sumac with vigor. Recovery activities planned or under way include additional surveys, habitat protection, and genetic studies to determine if hybridization occurs between R. michauxii and the common smooth sumac (R. glabra ). A global positioning system is being used to record species locations into a geographic information system. Graduate studies are planned to determine levels and viability of seed germination, and the feasibility of propagating and transplanting Michaux's sumac to establish or augment populations. The army also plans to set up and monitor prescribed burning plots to determine the best habitat management strategy for this species.

The first reintroduction of Michaux's sumac is doing well. The Georgia Heritage Inventory and Woodlanders (an Aiken, South Carolina, commercial nursery that specializes in native plants) cooperated in the transplant effort.

Contacts

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8300
http://www.northeast.fws.gov/

U.S. Fish and Wildlife Service
330 Ridgefield Court
Asheville, North Carolina 28806
Telephone: (704) 665-1195

Reference

U.S. Fish and Wildlife Service. 28 September 1989. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for Rhus michauxii. " Federal Register 54 (187): 39853-39857.