''Dodecahema'' is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s in the family
Polygonaceae
The Polygonaceae are a Family (biology), family of flowering plants known Common name, informally as the knotweed family or smartweed—buckwheat family in the United States. The Botanical name, name is Basionym, based on the genus ''Polygonum'', ...
with a single
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
restricted to
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, where it is an
endangered species
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
on the state and federal levels. Its common name is slender-horned spineflower. This is a small annual plant forming a patch of spreading basal leaves a few centimeters in diameter, or slightly larger when more moisture is available. It bolts an erect stalk upon which it bears
inflorescence
In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...
s of flowers. Each group of white or pink flowers is enclosed in a tiny cup of fused
bract
In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale.
Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...
s which is only a few millimeters wide. The fruit is a dark
achene
An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple fruit, simple dry fruits, dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and Dehi ...
about 2 millimeters long.
This plant grows in the
silt-rich floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
s and
washes of the foothills of the
Transverse Ranges
The Transverse Ranges are a group of mountain ranges of Southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Ba ...
and the
Peninsular Ranges
The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Pacific Coast Range ...
of
southern California
Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...
. It is known from fewer than 40 reported sightings, many of which were in locations that have since been claimed for development or otherwise altered. About 19 occurrences are believed to exist now.
[''Dodecahema leptoceras''.]
The Nature Conservancy. This plant has been recorded in only a few general areas, including
Tujunga Wash
Tujunga Wash is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed March 16, 2011 stream in Los Angeles County, California. It is a tributary of the Los Angeles River, providing about a f ...
and the floodlands surrounding the
Santa Ana and
San Jacinto Rivers. The main threats to this species include water diversion,
off-road vehicles
An off-road vehicle (ORV), also known as an off-highway vehicle (OHV), overland vehicle or adventure vehicle, is a type of transportation specifically engineered to navigate unpaved roads and surfaces. These include trails, forest roads, and o ...
,
invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
of plants, and development on the private property where most occurrences of this plant are located.
References
External links
Jepson Manual TreatmentUSDA Plants ProfileFlora of North AmericaPhoto gallery
{{Taxonbar, from1=Q2594241, from2=Q15591208
Endemic flora of California
Monotypic Polygonaceae genera