|Listed||January 21, 1987|
|Description||Annual herb with small oblong leaves and white four-petaled flowers.|
|Habitat||Sand pine scrub.|
|Threats||Agricultural and residential development, fire suppression.|
Carter's mustard, Warea carteri, is an unbranched annual plant with an erect stem about 3 ft (1m) tall. Alternate leaves gradually diminish in size as they ascend the stem, then gather into small bracts toward the top of the plant. White, four-petaled flowers are borne in a loose cluster (raceme) at the end of the stem. The fruit, a large seed pod on a slender stalk, is dry and splits apart to shed seeds.
Germination is unknown but may occur in spring. Leafing in this species may occur in summer. Anthesis occurs in late September to early October, sporadically all year. Both fruiting and seed dispersal are believed to occur in October.
Carter's mustard is found in sand pine scrub along the Lake Wales Ridge, an area that includes the cities of Lake Wales, Avon Park, Sebring, and Lake Placid, and extends as far south as the small town of Venus. Sand pine scrub burns infrequently, roughly every 30 years, but the fires are intense. Most shrubs in this type of habitat renew themselves from root sprouts, but sand pine and rosemary-dominant plants in sand pine scrub repopulate burned-over areas only by seed.
Florida sand pine scrub supports dozens of endemic plants that are becoming increasingly rare or endangered.
Between 1878 and 1934, many herbarium collections of Carter's mustard were made from both pine rockland and scrub in Dade County, Florida. Careful searches have failed to relocate this plant in remaining fragments of Dade County pine rockland, and it appears to have been eliminated by urbanization.
From 1922 to 1967 Carter's mustard was collected from scrub in Polk and Highlands counties and reported from Liberty and Brevard counties. A 1983 inventory of scrubland found Carter's mustard near Lake Josephine in Highlands County, a site now being developed for housing. Six biological preserves and one federal installation in Polk and Highlands counties contain sand pine scrub vegetation, but apparently no Carter's mustard.
Carter's mustard is known today from two sites in northeastern Polk County and from two sites in Highlands County—northeast of Sebring, and from the Archbold Biological Station. Of these four sites, only the population on Archbold Biological Station is protected. There, it occurs in Florida rosemary evergreen oak scrub vegetation, in thickets of inopina oak with South Florida slash pine (called "scrubby flatwoods"), and in flatwoods.
Much of the original sand pine scrub habitat in south-central Florida has been lost to agricultural and residential development. Remaining habitat is often fragmented and degraded by human disturbance or by suppression of fire, which allows woody vegetation to overwhelm plants of earlier successional stages. Carter's mustard is particularly vulnerable to off-road vehicles that drive through the open spaces between shrubs.
Conservation and Recovery
The Archbold Biological Station conducts periodic burning and other conservation practices that will assist this population of Carter's mustard in its recovery. Larger areas of sand pine scrub need to be acquired, however, if this plant is to survive over the long term. Land acquisition of sand scrub parcels in Highlands and Polk counties by the Florida Natural Areas Inventory should remove some of the developmental dangers to threatened scrub species.
In 1995, the U. S. Fish and Wildlife Service (FWS) announced a draft of the "Recovery Plan for Nineteen Florida Scrub and High Pineland Plants," which outlines necessary efforts to restore Carter's mustard and other endangered plants. Among these are: habitat protection through land purchase and other means (including the Habitat Conservation Plan process for threatened animals in the Florida scrub habitat); the management of protected habitats; and the assessment of progress and plan post-recovery monitoring.
This plan is a revision and expansion of a 1990 recovery plan which originally covered 11 plant species. The 1990 version emphasized the need for land acquisition to protect these plants. At the time, the state and private organizations had already made significant acquisitions, and more have been accomplished since then (including initial land purchase for the Lake Wales Ridge National Wildlife Refuge). These land purchases, accompanied by the other elements of the recovery plan, are likely to assure the full recovery or at least the downlisting of the large majority of the 19 plants, including Carter's mustard.
Regional Office of Endangered Species
U.S. Fish and Wildlife Service
1875 Century Blvd, Suite 200
Atlanta, Georgia 30345
Abrahamson, W. G. 1984. "Post-Fire Recovery of the Florida Lake Wales Ridge Vegetation." American Journal of Botany 71:9-21.
Abrahamson, W. G., et al. 1984. "Vegetation of the Archbold Biological Station, Florida." Florida Scientist 47:209-250.
Meyers, R. 1985. "Fire and the Dynamic Relationship between Florida Sandhill and Sand Pine Scrub Vegetation." Bulletin of the Torrey Botanical Club 112:241-252.
Wunderlin, R. P. 1982. Guide to the Vascular Flora of Central Florida. University Presses of Florida, Gainesville.