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poisonous 

gray horsebrush

Tetradymia canescens

family: Asteraceae 

Native Perennial 

Distribution: Western U.S.,

western Canada

Plant Communities: grasslands,

sagebrush, desert shrub, PJ,

chaparral, forests

Soil Types: medium to coarse

soils (prefers gravelly soil or

sandy loams)

Location: slopes, ridgetops, hills,

plains at 1,300 to 10,800 ft.

elevation'

• Inflorescence

• Heads 5-20

• 4 phyllaries (bracts under flower head)

• Leaves

• Alternate, simple with woolly surfaces

• Prominent midvein

• Stems gray in color

• Bark shreddy

Important

Tetradymia canescens – IdentificationFlickr “Tetradymia canescens” images courtesy of Matt Lavin.

Characteristic Growth FormFlickr “Tetradymia canescens” images courtesy of Matt Lavin.

Characteristic Growth Form■

Tetradymia canescens –

herbarium sample

Sample showing typical stems:

Stems highly branched, new growth

silvery canescent tomentose.

Simple leaves, woolly-canescent, silvery.

Flowers: heads with 4 phyllaries, disk

florets bright yellow.Tetradymia canescens - Autecology

Plant Attributes

•Warm season shrub

•Relatively deep taproot

•Insect pollinated (moths, bees, flies, beetles)

•High seed production

•Low seedling survival, slow population turnover

•Regeneration by resprouting from root crown

•Occurs in all successional stagesTetradymia canescens - Autecology

Forage Quality, Palatability, and Cover

• Poor value as livestock forage species

•Toxic to sheep, with small amounts (.5% body weight)

causing liver damage, capillary breakage, and head

swelling

•Can cause abortion and poor wool quality

•Low palatability for livestock and wildlife

•Low in energy and protein content

•Can provide fair cover/habitat for large mammals and

good cover for small mammals and birdsTetradymia canescens - Autecology

Drought / Stress Tolerance

•Highly drought tolerant

Grazing Tolerance

•Increaser with high intensity grazing

Fire Tolerance

•Fire resistant shrub

•Rapid resprouting following fire