''Ceanothus pauciflorus'', known by the common name Mojave ceanothus, is a species of flowering

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

in the

buckthorn ''Rhamnus'' is a genus of about 110 accepted species of shrubs or small trees, commonly known as buckthorns, in the family Rhamnaceae. Its species range from tall (rarely to ) and are native mainly in east Asia and North America, but found thr ...

family,

Rhamnaceae The Rhamnaceae are a large family of flowering plants, mostly trees, shrubs, and some vines, commonly called the buckthorn family. Rhamnaceae is included in the order Rosales. The family contains about 55 genera and 950 species. The Rhamnaceae h ...

. It is native to the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

( Arizona, California, New Mexico, Texas, and Utah) and Mexico, where it grows primarily in

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity. It m ...

communities at moderate to high elevations. It is characterized by oppositely arranged leaves, corky stipules and white flowers. It was formerly known as ''Ceanothus greggii''.

Description

''Ceanothus pauciflorus'' is a many-branched shrub with woody parts that are gray in color and somewhat woolly. The flowers bloom in spring.Blakely, Larry
Desert Ceanothus, Ceanothus greggii A. Gray var. vestitus (E. Greene) McMinn (Rhamnaceae)
, Who's in a Name? People Commemorated in Eastern Sierra Plant Names Blooms are considered highly fragrant. ''C. pauciflorus'' is eagerly browsed by livestock and wild ungulates such as mule deer and desert bighorn sheep.

Morphology

This species is a

, around 0.2 to 4 m tall. The

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

is ascending to erect, and generally branches from at or near the base. The twigs are colored a pale gray to more or less white, and are densely

puberulent Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

to short-tomentose. The evergreen leaves are arranged oppositely, on a petiole 1 to 3 mm long, and with a leaf blade 5 to 20 mm long by 3 to 19 mm wide. The adaxial surface of the leaf is concave, colored gray-green to yellow-green, and puberulent, becoming glabrous (smooth) in age. The abaxial surface of the leaf is convex, colored gray-green, and is glabrous or has short, curly hairs. The tip of the leaf is generally shaped acute to obtuse. The margins of the leaf may have teeth. The stipule is a knob-like structure. The inflorescence is a small (less than 2 cm long) cluster of many white flowers on short lateral branches. The fruit is a horned capsule a few millimeters wide which bursts explosively to expel the three seeds inside, which require thermal scarification from wildfire before they can germinate.

Taxonomy

This species is a member of the ''Ceanothus''

subgenus In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between t ...

''Cerastes''.

Classification

This species was originally discovered to science by Spanish botanists Martín Sessé y Lacasta and

José Mariano Mociño José Mariano Mociño Suárez Lozano (24 September 1757 – 12 June 1820), or simply José Mariano Mociño, was a naturalist from New Spain. After having studied philosophy and medicine, he conducted early research on the botany, geology, and ant ...

on an expedition to western Mexico in 1790 to 1791. It was later described as ''Ceanothus pauciflorus'' by Augustin Pyramus de Candolle in 1825, based on the illustrations made by Sessé and Mociño expedition. Sessé and Mociño also collected a flowering specimen of ''Ceanothus'', later determined to be ''Ceanothus pauciflorus.'' Because ''Ceanothus pauciflorus'' was the first description of the plant, subsequent descriptions were reduced to synonyms. It was named by

Asa Gray Asa Gray (November 18, 1810 – January 30, 1888) is considered the most important American botanist of the 19th century. His ''Darwiniana'' was considered an important explanation of how religion and science were not necessarily mutually excl ...

of Harvard University in 1853 as ''Ceanothus greggii'' in honor of its collector,

Josiah Gregg Josiah Gregg (19 July 1806 – 25 February 1850) was an American merchant, explorer, naturalist, and author of '' Commerce of the Prairies'', about the American Southwest and parts of northern Mexico. He collected many previously undescribed pla ...

, who found the plant in 1847 at the site of the Battle of Buena Vista in the Mexican state of

Coahuila Coahuila (), formally Coahuila de Zaragoza (), officially the Free and Sovereign State of Coahuila de Zaragoza ( es, Estado Libre y Soberano de Coahuila de Zaragoza), is one of the 32 states of Mexico. Coahuila borders the Mexican states of N ...

during the Mexican–American War. Edward Lee Greene named it as ''Ceanothus vestitus'', but recent taxonomic analysis finds that ''C. vestitus'' does not have enough morphological evidence to warrant a separate taxon from ''C. pauciflorus''.

Distribution and habitat

''Ceanothus pauciflorus'' is widely distributed throughout the

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

and northern Mexico. In the United States, it is found in the states of Arizona, California, Nevada, New Mexico, Texas, and Utah. It is widely distributed in Mexico, found from Baja California and

south to Oaxaca. In Baja California, it is found from the Sierra Juarez to the

Sierra de la Asamblea The Sierra de La Asamblea, also referred to as San Luis, Sierra de Yuba, or Sierra de Jubai, is an isolated mountain range in Baja California. The range reaches a height of 1,661 metres, and is separated from southernmost end of the Sierra de San ...

. However, it is replaced in a portion of its range in California and Baja California with a close relative, ''

Ceanothus perplexans ''Ceanothus perplexans'', commonly known as cup-leaved ceanothus, is a species of flowering shrub in the Rhamnaceae (buckthorn) family. It is native to California, southwestern Arizona, and Baja California. Description ''Ceanothus perplexans' ...

''. This species is found on a variety of habitats over its wide distribution, although it is almost always found in shrub-dominated communities like

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

and matorral at moderate to high elevations (550 to 2600 m).

References

External links

Calflora Database: ''Ceanothus greggii'' (desert ceanothus)Jepson Manual treatment of ''Ceanothus greggii''USDA Plants Profile for ''Ceanothus greggii'' (desert ceanothus)UC Photos gallery — ''Ceanothus greggii''
{{Taxonbar, from=Q59420238 pauciflorus Flora of California Flora of Northeastern Mexico Flora of Northwestern Mexico Flora of the South-Central United States Flora of the Southwestern United States Flora of the California desert regions Flora of the Sierra Nevada (United States) North American desert flora Natural history of the California chaparral and woodlands Natural history of the Mojave Desert Natural history of the Peninsular Ranges Natural history of the Transverse Ranges Plants described in 1825 Taxa named by Augustin Pyramus de Candolle Flora without expected TNC conservation status