Trillium albidum

Trillium albidum, also known as giant white wakerobin,[3] white toadshade,[4] and sweet trillium, is a species of flowering plant in the family Melanthiaceae. The species is endemic to the western United States, ranging from west central California through Oregon to Washington.[5][6] It 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.[4]

Trillium albidum
Mendocino County, California

Apparently Secure  (NatureServe)[1]
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Liliales
Family: Melanthiaceae
Genus: Trillium
Species:
T. albidum
Binomial name
Trillium albidum
J. D. Freeman, 1975
Synonyms[2]
  • Trillium parviflorum V.G.Soukup (syn of Trillium albidum subsp. parviflorum)

In his authoritative treatment of 1975, Freeman noted that Trillium albidum "has been treated under the misapplied epithet "chloropetalum" for more than half a century."[7] In the area surrounding San Francisco Bay, where the ranges of T. albidum and T. chloropetalum overlap, identification is difficult.[8] The intermediate populations in this region may be due to hybridization of the two species.[9]

Taxonomy

In addition to Trillium albidum J.D.Freeman, the following infraspecific names are accepted by most naming authorities:

  • Trillium albidum subsp. albidum[10]
  • Trillium albidum subsp. parviflorum (V.G.Soukup) K.L.Chambers & S.C.Meyers[11][12]

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 17 to 30 cm (6.5 to 12 in) high (which is half of subsp. albidum) while the petals are just 2.2 to 4.5 cm (1 to 2 in) long and 0.4 to 1 cm (0 to 0.5 in) wide (which is consistently shorter and narrower than those of subsp. albidum).[4][13]

In 2002, Case described two distinct but related Trillium species, T. albidum J.D.Freeman and T. parviflorum V.G.Soukup.[4][14] Some naming authorities still consider both of these species names to be valid[15] while other authorities consider the latter name to be a synonym for T. albidum subsp. parviflorum,[16][17] 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.[18]

Geographically, T. 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 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.[14][19]

Description

Trillium albidum is a perennial herbaceous plant that spreads 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 blades are green and weakly mottled with brown or dark green spots (which often fade later in the season).[4]

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 is the only sessile-flowered Trillium species characterized by white flowers.[7] For most of its range, this characteristic is sufficient to identify the species. In the San Francisco Bay Area, where a variety of T. chloropetalum with white flower petals occurs, T. albidum is recognized by its reproductive organs, which are almost invariably pale green, with occasional purple stain.[20]

This plant has gained the Royal Horticultural Society's Award of Garden Merit.[21]

Ecology

Flowering typically occurs in the spring, from mid March to early May. In California, flowers bloom between February and June.[22]

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.[23] It has an indefinite life span of many years.

Bibliography
  • Case, Frederick W.; Case, Roberta B. (1997). Trilliums. Portland, Oregon: Timber Press. ISBN 978-0-88192-374-2.CS1 maint: ref=harv (link)
  • Freeman, J. D. (1975). "Revision of Trillium subgenus Phyllantherum (Liliaceae)". Brittonia. 27: 1–62. doi:10.2307/2805646.CS1 maint: ref=harv (link)

References
  1. "Trillium albidum". NatureServe Explorer. NatureServe. Retrieved 8 November 2019.
  2. "Trillium albidum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  3. "Trillium albidum". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 15 December 2015.
  4. Case Jr., Frederick W. (2002). "Trillium albidum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 26. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  5. "Trillium albidum". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved 12 August 2019.
  6. "Trillium albidum". Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the Consortium of California Herbaria. Berkeley, California: The Calflora Database – via www.calflora.org.
  7. Freeman (1975), p. 51.
  8. Case & Case (1997), pp. 160-161.
  9. Freeman (1975), pp. 53-54.
  10. "Trillium albidum subsp. albidum". Plants of the World Online. Retrieved 12 August 2019.
  11. "Trillium albidum subsp. parviflorum". Plants of the World Online. Retrieved 12 August 2019.
  12. "Trillium albidum subsp. parviflorum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  13. Dusek, Edith (Fall 1980). "Trilliums Western Style" (PDF). Bulletin of the American Rock Garden Society. 38 (4): 157–167. Retrieved 19 October 2019.
  14. Case Jr., Frederick W. (2002). "Trillium parviflorum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 26. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  15. "Trillium". The Plant List. Missouri Botanical Garden. Royal Botanic Gardens, Kew. Retrieved 12 August 2019.CS1 maint: others (link)
  16. "Trillium parviflorum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
  17. 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.
  18. 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.
  19. Bledsoe, Karen E. (1993). Morphological and cytological variation in ‘’Trillium albidum’’ Freeman (Liliaceae) (MA). Oregon State University. Retrieved 2019-10-19.
  20. Case & Case (1997), p. 158.
  21. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. November 2018. Retrieved 17 August 2019.
  22. 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.
  23. 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. Retrieved 25 October 2019.
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