Toad-flax Cress

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Toad-flax Cress

Schoenocrambe suffrutescens

ListedOctober 6, 1987
FamilyCruciferae (Brassicaceae)
DescriptionA perennial, herbaceous plant.
HabitatSemi-desert scrub.
ThreatsHabitat destruction and disturbance, and intrinsic risks of only three small populations.


The toad-flax cress, also known as shrubby reed-mustard, is a perennial, herbaceous plant. It has clumped stems that grow as tall as 10 in (25 cm) and arise from a branching, woody root crown. Its leaves have a smooth margin, and are 0.4-1.0 in (10-25 mm) long and 0.12-0.40 in (3-10 mm) wide. The leaves are arranged in alternate fashion on the stem, and are attached by a short petiole. The flowers have light-yellow or greenish-yellow petals, and measure about 0.4 in (10 mm) wide. The flowers are arranged in an open inflorescence (a raceme) at the top of the stem, containing 5 to 20 flowers.


The toad-flax cress occurs in fine-grained, clay-rich soil containing bits of white shale and volcanic tuff. Its sites are on level to moderately sloping ground in semi-desert shrub vegetation.


The toad-flax cress is a local (or endemic) species of the Colorado River drainage of eastern Utah. It occurs in the south-central Uintah Basin near the Green River in Uintah County.


The toad-flax cress is known from only three populations, with a total abundance of about 5,000 individuals. One population is in the Gray Knolls between the Green River and Hill Creek, and supports about 1,000 plants. This site is partially on the Uintah and Ourlay Reservation of the Ute Indian tribe, and partially on the Naval Oil Shale Reserve Number 2 administered by the federal Department of Energy. A second site is centered on Little Pack Mountain and supports about 3,000 plants. This site is partially on the Uintah and Ourlay Reservation, partially on Bureau of Land Management lands, and the rest on private land. The third site is located at the base of the Bad Lands Cliff and contains about 1,000 plants. This site is entirely on Bureau of Land Management lands. The toad-flax cress is thought to have declined significantly from its historical range and abundance. Its habitat is vulnerable to damage caused by activity related to the exploration and exploitation of oil, oil-shale, and gas resources. Its habitat is also underlain by deposits of volcanic rock of potential use as building stone. Other threats are associated with the use of off-road vehicles in its habitat, trampling by hikers, and grazing by domestic livestock. There are also intrinsic risks associated with the species having only three small populations, which could be devastated by an unpredictable catastrophe, such as an extreme weather event.

Conservation and Recovery

The U. S. Fish and Wildlife Service has developed a recovery plan for the toad-flax cress. The initial goal is to increase its abundance to supporting more than 2,000 individuals at each of its three separate populations. The longer-term goal is to have 10 populations with more than 2,000 plants each. These goals will be achieved by protecting the known populations from destruction or damage caused by hydrocarbon exploration and extraction activities, and by discovering or establishing new populations. Livestock grazing of the rare plant on the Uintah and Ourlay Reservation should be prevented, perhaps by fencing off the critical habitat. Associated activities include population monitoring, and research into the biology and habitat needs of the endangered plant.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 25486
Denver Federal Center
Denver, Colorado 80225

U. S. Fish and Wildlife Service, Ecological Services
145 East 1300 South Lincoln Plaza, Suite 404
Salt Lake City, Utah 84115-6110
Telephone: (801) 524-5009
Fax: (801) 524-5021


U. S. Fish and Wildlife Service. 1994. Utah Reed-Mustards: Clay Reed-Mustard (Schoenocrambe argillacea ); Barneby reed-mustard (Schoenocrambe barnebyi ); Shrubby Reed-Mustard (Schoenocrambe suffrutescens ). Region 6, Fish and Wildlife Service, Denver, CO.