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Trillium albidum

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Trillium albidum
Mendocino County, California

Apparently Secure  (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Liliales
Family: Melanthiaceae
Genus: Trillium
Species:
T. albidum
Binomial name
Trillium albidum
Synonyms[3]
T. albidum subsp. parviflorum
    • Trillium parviflorum V.G.Soukup

Trillium albidum is a species of flowering plant in the bunchflower family Melanthiaceae. It is the only trillium characterized by a stalkless white flower. The species is endemic to the western United States, ranging from central California through Oregon to southwestern Washington. In the San Francisco Bay Area, it is often confused with a white-flowered form of Trillium chloropetalum. In northern Oregon and southwestern Washington, it has a smaller, less conspicuous flower.

Trillium albidum was first described by John Daniel Freeman in 1975. The specific epithet albidum means "white", a reference to the uniformly white flower color of this distinctive species. It is commonly known as the giant white wakerobin or white toadshade.[4][5]

Description

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Trillium albidum is a perennial herbaceous plant that persists by means of underground rhizomes. There are three large leaf-like bracts arranged in a whorl about a scape that rises directly from the rhizome, growing to 22 to 58 cm (8.5 to 23 in) in height. The bracts are sessile and broadly ovate, each 10 to 20 cm (4 to 8 in) long and 12 to 15 cm (4.5 to 6 in) wide. The bracts are green and weakly mottled with brown or dark green spots (which often fade later in the season).[5]

Each stem produces one flower, which is held on top of the bracts. The fragrant flower has three lance-shaped green sepals and three wider white (sometimes pink or purple-tinged) petals measuring 4.8 to 8 cm (2 to 3 in) long and 2.2 to 3 cm (1 to 1 in) wide (although there is a conspicuously small-flowered subspecies as noted in the previous section).

Trillium albidum subsp. albidum and T. albidum subsp. parviflorum are distinguished on the basis of multiple characters:[5][6][7]

Trillium albidum subsp. albidum Trillium albidum subsp. parviflorum
Distribution South of Corvallis, Oregon North of the Columbia River
Stem count Often several from the same rhizome; large clumps are common ⇨ One (rarely more)
Stem length Longer: 22 to 58 cm (8.7 to 22.8 in) long ⇦ Shorter: 17 to 30 cm (6.7 to 11.8 in) long
Leaf mottling Immaculate to lightly mottled ⇨ Lightly to heavily mottled, less commonly immaculate
Leaf size Larger: 10 to 20 cm (3.9 to 7.9 in) long and 12 to 15 cm (4.7 to 5.9 in) wide ⇦ Smaller: 6.5 to 16 cm (2.6 to 6.3 in) long and 5 to 8 cm (2.0 to 3.1 in) wide
Sepals (fruiting stage) Erect with tips touching or crossed over fruit ⇦ Cupped at fruit base before flaring widely outward
Petal size Longer and wider: 4.8 to 8 cm (1.9 to 3.1 in) long and 2.2 to 3 cm (0.9 to 1.2 in) wide ⇦ Shorter and narrower: 2.2 to 4.5 cm (0.9 to 1.8 in) long (rarely longer) and 0.4 to 1 cm (0.2 to 0.4 in) wide
Petal shape Widest near the middle, narrowing about equally in both directions ⇦ Narrow, appearing almost straight-sided
Petal attachment Constricted strongly at the base ⇨ No noticeable constriction at the base
Fruit color Green or purplish green ⇨ Dark reddish purple or maroon
Fruit surface Dull ⇦ Glossy to shiny
Fruit shape Triangular; more or less prominently ridged top to bottom resulting in a series of planes; taller than wide ⇦ Round; ridging (if any) confined to the top of the fruit; no indication of planes; wider than tall
Scent Strongly rose (funereal) ⇦ ⇨ Lightly bitter or spicy-rank, clove-like

In the region between Corvallis, Oregon and the Columbia River, the species is variable and difficult to identify to subspecies level. The directional arrows in the table above point toward the subspecies that dominates with respect to that character.[7]

Trillium albidum is the only sessile-flowered Trillium species characterized by white flowers. Throughout most of its range, this characteristic is sufficient to identify the species, but in the San Francisco Bay Area where both T. albidum and a white-flowered variety of T. chloropetalum occur, the two species are distinguished by their reproductive organs. The latter has dark purple stamens and carpels while those of T. albidum are almost invariably white or pale green, with occasional purple stain.[8][9]

This plant has gained the Royal Horticultural Society's Award of Garden Merit.[10][11]

Taxonomy

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Trillium albidum was one of five new species described by John Daniel Freeman in 1975 (the others being T. decipiens, T. foetidissimum, T. kurabayashii, and T. reliquum).[12] The specific epithet albidum, which means "white",[13] refers to its uniformly white flower. Despite being one of the most distinctive species in subgenus Sessilia, the taxon was treated under the misapplied epithet chloropetalum for almost 75 years. To alleviate the confusion, Freeman gave a completely new treatment of Trillium chloropetalum (Torr.) Howell that dissociated the latter from T. albidum.[14]

The following infraspecific names are accepted by most naming authorities:[15][3]

  • Trillium albidum subsp. albidum
  • Trillium albidum subsp. parviflorum (V.G.Soukup) K.L.Chambers & S.C.Meyers

The two subspecies are distinguished by overall size as well as the size and shape of the flower petals. In subsp. parviflorum, the scape is just half the length of the typical subspecies while the petals are consistently shorter and narrower.

In 2002, Case described two distinct but related Trillium species, T. albidum J.D.Freeman and T. parviflorum V.G.Soukup.[5][6] Some naming authorities still consider both of these species names to be valid[16] while other authorities consider the latter name to be a synonym for T. albidum subsp. parviflorum,[17][18] in which case the two species originally described by Case become a single species. In any case, there is evidence that T. albidum and T. albidum subsp. parviflorum are less closely related to each other than the latter is to T. luteum, a sessile trillium species native to eastern North America.[19]

Distribution and habitat

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Trillium albidum has the widest range of any sessile-flowered trillium in western North America, from central California through Oregon to southwestern Washington.[20][21] In northern California, its range extends eastward from the Pacific coast through the Klamath Mountains into the Sierra Nevada. The type specimen was collected in Josephine County in southern Oregon. The southern edge of its range overlaps with that of T. chloropetalum in the San Francisco Bay Area. The intermediate populations found in this region may be due to hybridization of the two species.[22][23]

The typical subspecies Trillium albidum subsp. albidum ranges from northern California to central Oregon while T. albidum subsp. parviflorum is found in northwestern Oregon and southwestern Washington. In the region where the two subspecies overlap, from the Umpqua River north to the Columbia River, there are populations of considerable variation, which complicates identification at the subspecies level based on morphological characters alone.[6][24] In southwestern Oregon, just north of the California line, there is a population of plants with flowers that are pale yellow or creamy (not white) with no purple pigments whatsoever. Since these plants grow at the higher elevations, flowering is delayed to May or early June.[25] Evidently this taxon has not been named.

Trillium albidum is found in diverse habitats, on the moist slopes of mixed deciduous-coniferous forests, among shrubs and thickets, and along stream banks and river beds.[5]

Ecology

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Flowering typically occurs in the spring, from mid March to early May. In California, flowers bloom between February and June.[26]

Like other Trillium species, T. albidum has a one-leaf vegetative stage followed by a three-leaf vegetative (juvenile) stage. After several years of vegetative growth, the plant finally reaches its three-leaf reproductive (flowering) stage.[27] It has an indefinite life span of many years.

Conservation

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The global conservation status of Trillium albidum is apparently secure (G4).[1] However, Trillium albidum subsp. parviflorum is globally imperiled (T2).[28]

References

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  1. ^ a b "Trillium albidum". NatureServe Explorer. NatureServe. Retrieved 6 March 2022.
  2. ^ "Giant White Wakerobin (Trillium albidum)". The IUCN Red List of Threatened Species, Version 2022-2. Retrieved 28 March 2023.
  3. ^ a b "Trillium albidum subsp. parviflorum". Plants of the World Online. Retrieved 12 August 2019.
  4. ^ NRCS. "Trillium albidum". PLANTS Database. United States Department of Agriculture (USDA). Retrieved 6 March 2022.
  5. ^ a b c d e Case Jr., Frederick W. (2002). "Trillium albidum". 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 25 March 2022 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  6. ^ a b c Case Jr., Frederick W. (2002). "Trillium parviflorum". 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 25 March 2022 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  7. ^ a b Dusek, Edith (Fall 1980). Foster, Laura Louise (ed.). "New Trillium Species Named" (PDF). Bulletin of the American Rock Garden Society. 38 (4): 167–169. Retrieved 24 March 2022.
  8. ^ Freeman (1975), p. 51.
  9. ^ Case & Case (1997), p. 158.
  10. ^ "Trillium albidum". www.rhs.org. Royal Horticultural Society. Retrieved 5 March 2021.
  11. ^ "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. November 2018. Retrieved 17 August 2019.
  12. ^ Freeman (1975).
  13. ^ Gledhill, David (2008). The Names of Plants (4th ed.). Cambridge University Press. p. 41. ISBN 978-0-521-86645-3.
  14. ^ Freeman (1975), pp. 52–55.
  15. ^ "Trillium albidum subsp. albidum". Plants of the World Online. Retrieved 12 August 2019.
  16. ^ "Trillium". The Plant List. Royal Botanic Gardens, Kew. Retrieved 12 August 2019. Note that this website has been superseded by World Flora Online
  17. ^ "Trillium parviflorum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  18. ^ Chambers, Kenton L.; Meyers, Stephen C. (2011). "Nomenclatural changes for some taxa in the Oregon flora". Journal of the Botanical Research Institute of Texas. 5 (2): 619–623. ISSN 1934-5259.
  19. ^ 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.
  20. ^ "Trillium albidum". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved 6 March 2022.
  21. ^ "Trillium albidum". Calflora. Berkeley, California: The Calflora Database. Retrieved 6 March 2022.
  22. ^ Freeman (1975), pp. 53–54.
  23. ^ Case & Case (1997), pp. 160–161.
  24. ^ Bledsoe, Karen E. (1993). Morphological and cytological variation in Trillium albidum Freeman (Liliaceae) (MA). Oregon State University. Retrieved 2019-10-19.
  25. ^ Dusek, Edith (Fall 1980). "Trilliums Western Style" (PDF). Bulletin of the American Rock Garden Society. 38 (4): 157–167. Retrieved 24 March 2022.
  26. ^ McNeal, Dale W.; Ness, Bryan D. (2012). "Trillium albidum". In Jepson Flora Project (ed.). Jepson eFlora. The Jepson Herbarium, University of California, Berkeley. Retrieved 13 August 2019.
  27. ^ Kawano, Shoichi; Ohara, Masashi; Utech, Frederick H. (1992). "Life History Studies on the Genus Trillium (Liliaceae) VI. Life History Characteristics of Three Western North American Species and Their Evolutionary-Ecological Implications" (PDF). Plant Species Biol. 7: 21–36. doi:10.1111/j.1442-1984.1992.tb00239.x. Retrieved 25 October 2019.
  28. ^ "Trillium albidum". NatureServe Explorer. NatureServe. Retrieved 6 March 2022.

Bibliography

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