Pseudotrillium
Pseudotrillium rivale

Vulnerable  (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Liliales
Family: Melanthiaceae
Tribe: Parideae
Genus: Pseudotrillium
S.B.Farmer[2]
Species:
P. rivale
Binomial name
Pseudotrillium rivale
(S.Watson) S.B.Farmer[3]
Synonyms[4]
  • Trillium rivale S.Watson

Pseudotrillium is a monotypic genus of flowering plant in the family Melanthiaceae. Its sole species, Pseudotrillium rivale, is commonly known as the brook wakerobin.[5] It is endemic to the Siskiyou Mountains of southern Oregon and northern California. The Latin specific epithet rivale means “growing by streams”, with reference to a preferred habitat.[6]

Description

Pseudotrillium rivale is a perennial, herbaceous, flowering plant that persists by means of an underground rhizome. In general appearance, it is similar to a Trillium (and at one time, it belonged to that genus). It has a whorl of three bracts (leaves) and a single trimerous flower with three sepals, three petals, two whorls of three stamens each, and three carpels (fused into a single ovary with three stigmas). It differs from Trillium in that it has spotted petals, leathery leaves with a cordate base, and a continuously elongating pedicel. At the onset of anthesis, the pedicel rises above the leaves, but once the flower is pollinated, the pedicel elongates and declines below the leaves.[7]

Pseudotrillium rivale grows up to 20 cm (7.9 in) tall. The lance-shaped leaves are up to 11 cm (4.3 in) long with leaf stalks (called petioles) 1 to 3 cm (0.4 to 1.2 in) in length. The leaves are glossy blue-green with conspicuous silvery veins. The plant has a nodding, non-fragrant flower on a pedicel 2.5 to 11 cm (1.0 to 4.3 in) long. The flower has green sepals and pink-blushed white petals up to 3 cm (1.2 in) long and 2 cm (0.8 in) wide.[8][7]

Taxonomy

Pseudotrillium rivale was first described as Trillium rivale by American botanist Sereno Watson in 1885.[9] Its type specimen was collected in 1880 at Big Flat in the Siskiyou Mountains, thirty miles east of Crescent City, California.[10] 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 and molecular phylogenetic evidence, Trillium rivale was segregated into a monotypic genus by Susan B. Farmer in 2002.[11] For this purpose, Farmer simultaneously described the taxa Pseudotrillium and Pseudotrillium rivale.[2][3] As of March 2023, the name Pseudotrillium rivale (S.Watson) S.B.Farmer is widely recognized.[1][4][8][12][13]

Pseudotrillium is a member of tribe Parideae. It is sister to the remainder of Parideae, a clade that includes Paris and Trillium.[11] 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.[14]

Distribution

Pseudotrillium rivale is endemic to the Siskiyou Mountains of southern Oregon (Josephine, Coos, Douglas, and Curry counties) and northern California (Siskiyou and Del Norte counties), usually on soils of ultramafic origin, such as serpentine.[12][13] 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.[15]

Ecology

Pseudotrillium rivale flowers April to June,[8] with northern California plants flowering somewhat later than those in Oregon. At higher elevations, the onset of flowering may be delayed until early May.[16] 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.[7][15]

Uses

Under its former name, Trillium rivale, this plant has gained the Royal Horticultural Society's Award of Garden Merit.[17][18] Hardy down to −10 °C (14 °F), it requires a sheltered position in partial or full shade.[17]

References

  1. 1 2 "Pseudotrillium rivale". NatureServe Explorer. NatureServe. Retrieved 23 March 2022.
  2. 1 2 "Pseudotrillium S.B.Farmer". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 19 March 2023.
  3. 1 2 "Pseudotrillium rivale (S.Watson) S.B.Farmer". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 19 March 2023.
  4. 1 2 "Pseudotrillium rivale (S.Watson) S.B.Farmer". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 16 March 2023.
  5. ↑ USDA, NRCS (n.d.). "Trillium rivale". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 23 March 2022.
  6. ↑ Harrison, Lorraine (2012). RHS Latin for Gardeners. United Kingdom: Mitchell Beazley. ISBN 184533731X.
  7. 1 2 3 Case Jr., Frederick W. (2002). "Trillium rivale". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 26. New York and Oxford: Oxford University Press. Retrieved July 16, 2019 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  8. 1 2 3 Jepson Flora Project (ed.). "Pseudotrillium rivale". Jepson eFlora. The Jepson Herbarium, University of California, Berkeley.
  9. ↑ "Trillium rivale S.Watson". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 16 March 2023.
  10. ↑ Watson, Sereno (1885). "Contributions to American Botany". Proceedings of the American Academy of Arts and Sciences. Boston, Massachusetts. 20: 378. Retrieved 16 March 2023.
  11. 1 2 Farmer, Susan B.; Schilling, Edward E. (October 2002). "Phylogenetic Analyses of Trilliaceae based on Morphological and Molecular Data" (PDF). Systematic Botany. 27 (4): 674–692.
  12. 1 2 "Pseudotrillium rivale". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved 23 March 2022.
  13. 1 2 "Pseudotrillium rivale". Calflora. Berkeley, California: The Calflora Database. Retrieved 23 March 2022.
  14. ↑ Lampley (2021), pp. 1–16.
  15. 1 2 Dusek, Edith (Fall 1980). "Trilliums western style" (PDF). American Rock Garden Society Bulletin. 38 (4): 157–167. Retrieved 23 March 2022.
  16. ↑ Case & Case (1997), p. 133.
  17. 1 2 "Trillium rivale". www.rhs.org. Royal Horticultural Society. Retrieved 27 February 2020.
  18. ↑ "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. November 2018. Retrieved 17 August 2019.

Bibliography

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