Purshia
Encyclopedia
Purshia is a small genus of 5-8 species of flowering plant
s in the family Rosaceae
, native to western North America
, where they grow in dry climates from southeast British Columbia
in Canada
south throughout the western United States
to northern Mexico
. The classification of Purshia within the Rosaceae has been unclear. The genus was originally placed in the subfamily Rosoideae
, but is now placed in subfamily Dryadoideae
.
They are deciduous
or evergreen
shrub
s, typically reaching 0.3-5 m tall. The leaves
are small, 1-3 cm long, deeply three- to five-lobed, with revolute margins. The flower
s are 1-2 cm diameter, with five white to pale yellow or pink petals and yellow stamens. The fruit
is a cluster of dry, slender, leathery achene
s 2-6 cm long. The roots have root nodule
s that host the nitrogen-fixing
bacterium Frankia
.
The evergreen species were treated separately in the genus Cowania in the past; this genus is still accepted by some botanists.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s in the family Rosaceae
Rosaceae
Rosaceae are a medium-sized family of flowering plants, including about 2830 species in 95 genera. The name is derived from the type genus Rosa. Among the largest genera are Alchemilla , Sorbus , Crataegus , Cotoneaster , and Rubus...
, native to western North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, where they grow in dry climates from southeast 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...
in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
south throughout the western United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
to northern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. The classification of Purshia within the Rosaceae has been unclear. The genus was originally placed in the subfamily Rosoideae
Rosoideae
The rose subfamily Rosoideae consists of more than 850 species, including many shrubs, perennial herbs, and fruit plants such as strawberries and brambles...
, but is now placed in subfamily Dryadoideae
Dryadoideae
The Dryadoideae subfamily of the Rosaceae consists of four genera, all of which share root nodules that host the nitrogen-fixing bacterium Frankia. They are sub-shrubs, shrubs, or small trees with a base chromosome number of 9, whose fruits are either an achene or an aggregate of achenes....
.
They are deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
or evergreen
Evergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
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...
s, typically reaching 0.3-5 m tall. The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are small, 1-3 cm long, deeply three- to five-lobed, with revolute margins. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are 1-2 cm diameter, with five white to pale yellow or pink petals and yellow stamens. The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a cluster of dry, slender, leathery achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
s 2-6 cm long. The roots have root nodule
Root nodule
Root nodules occur on the roots of plants that associate with symbiotic nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia...
s that host the nitrogen-fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
bacterium Frankia
Frankia
Frankia is a genus of nitrogen fixing, filamentous bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobia bacteria that are found in the root nodules of legumes in the Fabaceae family. Bacteria of this genus also form root nodules.The genus Frankia was originally named by...
.
The evergreen species were treated separately in the genus Cowania in the past; this genus is still accepted by some botanists.
Species
- Purshia ericifolia - Heath Cliffrose. Texas.
- Purshia glandulosa - Desert Bitterbrush. Nevada, Utah, Arizona.
- Purshia mexicanaPurshia mexicanaPurshia mexicana is a species of perennial flowering small tree in the rose family known by the common name Mexican cliffrose. It is native to western-northern Mexico, the region of the Sierra Madre Occidental cordillera....
- Mexican Cliffrose (syn. Cowania mexicana). Mexico, Arizona. - Purshia pinkavae - Pinkava's Cliffrose. Arizona.
- Purshia plicata - Antelope Bush (syn. Cowania plicata). Mexico (Nuevo León).
- Purshia stansburianaPurshia stansburianaPurshia stansburyana is a species of flowering plant in the rose family known by the common name Stansbury's cliffrose...
- Stansbury Cliffrose (syn. P. mexicana var. stansburiana, Cowania stansburiana). Idaho south to California, Arizona and New Mexico. - Purshia subintegra (possibly a hybrid between P. pinkavae and P. stansburiana). Arizona.
- Purshia tridentataPurshia tridentataPurshia tridentata is a nitrogen fixing shrub in the genus Purshia, native to mountainous areas of western North America ranging from southeastern British Columbia in the north, east to Montana and south to California and New Mexico...
- Antelope Bitterbrush. British Columbia south to California and New Mexico.
External links
- Jepson Flora Project: Purshia (click 'next taxon' to see species accounts of Californian species)
- USDA Plants Profile: Purshia
- Germplasm Resources Information Network: Purshia