Vahl's Boxwood

Buxus vahlii

Description

Vahl's boxwood, Buxus vahlii, is an evergreen shrub or small tree that can grow up to 15 ft (4.6 m) high. Individual stems extend about 5 in (13 cm) before branching. Twigs show two characteristic grooves below each pair of leaves. Simple, opposite leaves are oblong to obovate, a shiny, dark green color, and up to 1.5 in (3.8 cm) long.

Vahl's boxwood reproduces by seed, which it produces in relatively large quantities. Light green flowers bloom in clusters from December to April. Clusters are often difficult to see because of their small size and location beneath foliage. A solitary female flower blooms at the tip, and several male flowers are borne on the stem just below it. The fruit is a tiny, three-horned capsule.

Habitat

Vahl's boxwood is restricted to limestone ravines and ledges in semi-evergreen forests along the coast at elevations below 330 ft (100 m). It prefers the heavy shade of the forest canopy and is often situated on steep, east-facing slopes.

The Punta Higuero site (see below) is a ravine located on the eastern end of a nuclear power plant; the Hato Tejas site is on hills surrounded by a large shopping center and industrial activities. Part of the east-facing slope containing this population has been mined for limestone and reduced to a narrow ledge. The Punta Higuero site has shallow, clay soil with an abundance of small limestone rocks over a limestone bedrock. The Hato Tejas ledge, where the boxwood grows, has very shallow, stony soil that is barren and dry.

Distribution

This species was originally thought to occur in St. Croix and on Jamaica, as well as in Puerto Rico, but this no longer appears to be correct. It has not been collected outside of Puerto Rico in recent times and is now considered restricted to the island.

At present, two isolated populations—separated by about 70 mi (110 km) of coastline—survive near Hato Tejas (west of Bayamon) and Punta Higuero (north of Rincon). Cultivated plants exist elsewhere in Puerto Rico.

In 1987, the Hato Tejas site consisted of about 25 healthy shrubs on privately owned land. The site is in a tract of remnant forest within a group of haystack hills—limestone hills with a characteristic haystack shape. The shrubs grow along the edge of an old limestone quarry, surrounded by a large shopping center and several commercial and industrial lots.

The Punta Higuero population was surveyed in 1987 when it consisted of 60 plants, many dwarfed and depleted of chlorophyll by salt spray and high winds. The site is owned by the commonwealth of Puerto Rico but is readily accessible to houses on adjacent private property. Residents keep goats that could seriously harm the boxwood if allowed to escape into the public area.

Threats

Much of the lowland, semi-evergreen forest along the northern coast of Puerto Rico was long ago logged or clear-cut to support agriculture. Once a fairly common constituent of the plant community, Vahl's boxwood has been virtually eliminated by deforestation. Because of current low numbers, fire poses a significant threat to both populations, particularly during the dry season. In spite of harsh conditions at the Punta Higuero site, the boxwood appears to be reproducing well. Surveys have located seedlings and plants of various sizes.

Conservation and Recovery

Because of its beauty and potential for professional cultivation as an ornamental plant, there is a society devoted to Vahl's boxwood cultivation. This society works to preserve the plant and discourages collection from the wild, an act prohibited under commonwealth law. Privately cultivated plants could be used to reestablish populations in the wild. Attempts to propagate the shrub from seed have been largely unsuccessful. Propagation with cuttings tends to be more successful.

The karst region of the coast is rugged enough that unreported populations of Vahl's boxwood might yet exist. Fish and Wildlife Service personnel will conduct surveys of potential habitat along the north coast. The Recovery Plan recommends fencing the Punta Higuero site and devising conservation agreements with private landowners.

Contacts

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

Caribbean Field Office
U.S. Fish and Wildlife Service
P.O. Box 491
Boquerón, Puerto Rico 00622

References

Little, E. L., R. O. Woodbury, and F. H. Wadsworth.1974. Trees of Puerto Rico and the Virgin Islands. Forest Service Agricultural Handbook No. 449. U.S. Department of Agriculture, Washington, D.C.

Vivaldi, J. L., and R. O. Woodbury. 1981. " Buxus vahlii baill." Status Report Submitted to the U.S. Fish and Wildlife Service, Maygaguez, Puerto Rico.