Tetradymia canescens
Encyclopedia
Tetradymia argyraea is a species of flowering plant in the aster family
known by the common names spineless horsebrush and gray horsebrush. It is native to western North America from British Columbia
to California
to New Mexico
, where it grows in sagebrush
, woodlands, forest, scrubby open plains, and other habitat. It is a bushy shrub
growing to 60 to 80 centimeters in maximum height with multibranched woody or semi-woody stems that grow from taproot
s. It is coated in woolly fibers with hairless strips at intervals along the branches. It has no spines. The lance-shaped leaves are no more than 4 centimeters long and woolly or silver-haired in texture. Longer-lived leaves are alternately arranged along the stem and smaller, shorter-lived leaves occur in clusters near the axils of the primary leaves. The inflorescence
bears usually three to six flower heads
which are each enveloped in four thick phyllaries
coated in white woolly hairs. Each head contains four tubular flowers in shades of pale to bright yellow, each measuring up to 1.5 centimeters long. Flowers are produced in summer. The fruit is an achene
which may be up to 1.5 centimeters long including its long pappus
of bristles.
The shrub is wildfire
-resistant, resprouting vigorously and increasing in herbage and seed production in seasons following a fire. Fire suppression efforts decrease the abundance of the shrub and frequent burns increase it.
The shrub is toxic
to sheep, causing photosensitivity
, bad wool
quality, abortion
, and death due to the presence of furanoeremophilanes. It causes a swelling of the head known as bighead disease.
Native American
groups used this plant for a number of medicinal purposes, including protection from ghost
s and witches.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common names spineless horsebrush and gray horsebrush. It is native to western North America from British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
to California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
to New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, where it grows in sagebrush
Sagebrush
Sagebrush is a common name of a number of shrubby plant species in the genus Artemisia native to western North America;Or, the sagebrush steppe ecoregion, having one or more kinds of sagebrush, bunchgrasses and others;...
, woodlands, forest, scrubby open plains, and other habitat. It is a bushy shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
growing to 60 to 80 centimeters in maximum height with multibranched woody or semi-woody stems that grow from taproot
Taproot
A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.Plants with taproots are difficult to transplant...
s. It is coated in woolly fibers with hairless strips at intervals along the branches. It has no spines. The lance-shaped leaves are no more than 4 centimeters long and woolly or silver-haired in texture. Longer-lived leaves are alternately arranged along the stem and smaller, shorter-lived leaves occur in clusters near the axils of the primary leaves. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
bears usually three to six flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
which are each enveloped in four thick phyllaries
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
coated in white woolly hairs. Each head contains four tubular flowers in shades of pale to bright yellow, each measuring up to 1.5 centimeters long. Flowers are produced in summer. The fruit is an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
which may be up to 1.5 centimeters long including its long pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
of bristles.
The shrub is wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
-resistant, resprouting vigorously and increasing in herbage and seed production in seasons following a fire. Fire suppression efforts decrease the abundance of the shrub and frequent burns increase it.
The shrub is toxic
Toxin
A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
to sheep, causing photosensitivity
Photosensitivity
Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light.- Human medicine :Sensitivity of the skin to a light source can take various forms. People with particular skin types are more sensitive to sunburn...
, bad wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
quality, abortion
Miscarriage
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
, and death due to the presence of furanoeremophilanes. It causes a swelling of the head known as bighead disease.
Native American
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
groups used this plant for a number of medicinal purposes, including protection from ghost
Ghost
In traditional belief and fiction, a ghost is the soul or spirit of a deceased person or animal that can appear, in visible form or other manifestation, to the living. Descriptions of the apparition of ghosts vary widely from an invisible presence to translucent or barely visible wispy shapes, to...
s and witches.