''Pseudotrillium'' is a

monotypic genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

in the bunchflower

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Melanthiaceae Melanthiaceae, also called the bunchflower family, is a family (biology), family of flowering plant, flowering herbaceous perennial plants native to the Northern Hemisphere. Along with many other lilioid monocots, early authors considered member ...

. Its sole

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), ...

, the

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

''Pseudotrillium rivale'', is commonly known as the brook wakerobin. It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the

Siskiyou Mountains The Siskiyou Mountains are a Coast Ranges, coastal subrange of the Klamath Mountains, and located in northwestern California and southwestern Oregon in the United States. They extend in an arc for approximately from east of Crescent City, Calif ...

of southern

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

and northern

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 ...

. The Latin

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''rivale'' means "growing by streams", a reference to a preferred habitat.

Description

''Pseudotrillium rivale'' is a

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of ...

that persists by means of an underground

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

. In general appearance, it is similar to a ''

Trillium ''Trillium'' (trillium, wakerobin, toadshade, tri flower, birthroot, birthwort, and sometimes "wood lily") is a genus of about fifty flowering plant species in the family Melanthiaceae. ''Trillium'' species are native to temperate regions of No ...

'' (and at one time, it belonged to that genus). It has a

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

of three

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 (leaves) and a single trimerous flower with three

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s, three

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s, two whorls of three

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s each, and three

carpel Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more ...

s (fused into a single

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

with three stigmas). It differs from ''Trillium'' in that it has spotted petals, leathery leaves with a

cordate Cordate is an adjective meaning ' heart-shaped' and is most typically used for: * Cordate (leaf shape), in plants * Cordate axe, a prehistoric stone tool See also * Chordate A chordate ( ) is a bilaterian animal belonging to the phyl ...

base, and a continuously elongating pedicel. At the onset of

anthesis Anthesis is the period during which a flower is fully open and functional. It may also refer to the onset of that period. The onset of anthesis is spectacular in some species. In ''Banksia'' species, for example, anthesis involves the extension ...

, the pedicel rises above the leaves, but once the flower is

pollinated Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; bird ...

, the pedicel elongates and declines below the leaves. ''Pseudotrillium rivale'' grows up to tall. The lance-shaped leaves are up to long with leaf stalks (called petioles) in length. The leaves are glossy blue-green with conspicuous silvery veins. The plant has a nodding, non-fragrant flower on a pedicel long. The flower has green sepals and pink-blushed white petals up to long and wide.

Taxonomy

''Pseudotrillium rivale'' was first described as ''Trillium rivale'' by American botanist

Sereno Watson Sereno Watson (December 1, 1826 – March 9, 1892) was an American botanist. Life Watson was born on December 1, 1826, in East Windsor Hill, Connecticut. Graduating from Yale in 1847 in biology, he drifted through various occupations unt ...

in 1885. Its

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

was collected in 1880 at Big Flat in the

, thirty miles east of

Crescent City, California Crescent City ( Tolowa: ''Taa-’at-dvn''; Yurok: ''Kohpey''; Wiyot: ''Daluwagh'') is the only incorporated city in Del Norte County, California, of which it is also the county seat. The city is on the North Coast of California and had a tota ...

. Watson compared the new species to the eastern '' Trillium nivale'', "which it much resembles in habit." Presumably he was referring to the tendency of the pedicel to decline below the leaves after pollination, a common habit of both species. Based on

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

and

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

evidence, ''Trillium rivale'' was segregated into a

by Susan B. Farmer in 2002. For this purpose, Farmer simultaneously described the taxa ''Pseudotrillium'' and ''Pseudotrillium rivale''. , the name ''Pseudotrillium rivale'' is widely recognized. ''Pseudotrillium'' is a member of tribe Parideae. It is

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to the remainder of Parideae, a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

that includes ''

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

'' and ''

''. Based on molecular phylogenetic studies, ''Pseudotrillium rivale'' is the first diverging ( basal) branch of Parideae, a result that is well supported. Historically, studies that omit this taxon have given strikingly different results, suggesting that "''Pseudotrillium'' could hold the key to phylogenetic studies" of Parideae.

Distribution

''Pseudotrillium rivale'' is

to the

of southern

( Josephine, Coos, Douglas, and

Curry Curry is a dish with a sauce or gravy seasoned with spices, mainly derived from the interchange of Indian cuisine with European taste in food, starting with the Portuguese, followed by the Dutch and British, and then thoroughly internatio ...

counties) and northern

( Siskiyou and Del Norte counties), usually on soils of

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usua ...

origin, such as serpentine. California plants, growing in a dense damp woods, are larger than Oregon plants in all respects with a strong tendency to produce colored flowers. In contrast, Oregon plants found in dry open woods are tiny plants with freckled white flowers.

Ecology

''Pseudotrillium rivale'' flowers April to June, with northern California plants flowering somewhat later than those in Oregon. At higher elevations, the onset of flowering may be delayed until early May. After flowering, the entire plant may enlarge and become more robust and turgid with very glossy leaves. Initially the pedicel is of moderate length but it soon begins to lengthen and twist in a most unusual way. If fertilization is successful, the pedicel arches downward so that the fruit comes in contact with the soil. By mid-July, the entire plant withers and goes dormant.

Uses

Under its former name, ''Trillium rivale'', this plant has gained the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...

Award of Garden Merit The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. It includes the full range of cultivated p ...

. Hardy down to , it requires a sheltered position in partial or full shade.

References

Bibliography

* *

External links

*
Calphotos Photo gallery, University of California: ''Trillium rivale''
Flora of the Klamath Mountains Flora of California Flora of Oregon Monotypic Liliales genera Melanthiaceae genera Plants described in 1885 {{Liliales-stub