Trillium ovatum
Pacific trillium blooming in Aldergrove Regional Park (British Columbia, Canada).
Conservation status
Secure  ( NatureServe) [1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Order:	Liliales
Family:	Melanthiaceae
Genus:	Trillium
Species:	T. ovatum
Binomial name
Trillium ovatum Pursh [2]
Synonyms [3] [4]
T. ovatum var. oettingeri Trillium ovatum subsp. oettingeri Munz & Thorne T. ovatum var. ovatum Trillium californicum Kellogg Trillium obovatum Hook. Trillium ovatum f. maculosum Case & R.B.Case Trillium ovatum var. stenosepalum R.R.Gates Trillium venosum R.R.Gates

Trillium ovatum, the Pacific trillium, also known as the western wakerobin, western white trillium, or western trillium, is a species of flowering plant in the family Melanthiaceae. ^{[1] [5] [6] [7]} It is found in western North America, from southern British Columbia and the tip of southwestern Alberta to central California, east to Idaho and western Montana. There is an isolated population in northern Colorado and southern Wyoming. ^[8]

T. ovatum is the most widespread and abundant trillium in western North America. ^[9] It is the only pedicellate-flowered Trillium species found within its range. ^[10] The type specimen for this species was gathered by Meriwether Lewis in 1806 along the Columbia River during the return trip of the Lewis and Clark Expedition. ^[11]

Description

The most widespread of the western North American trilliums, Trillium ovatum varies greatly within its range. Despite this, T. ovatum closely resembles the eastern T. grandiflorum. Apart from geographic location, the two species are not easily distinguished. ^[12]

T. ovatum is a perennial herbaceous plant that spreads by means of underground rhizomes. At maturity, each plant has one or two flowering scapes, each 20 to 50 cm (8 to 19.5 in) in length. The specific epithet ovatum means “egg-shaped,” which refers to the petals, not the leaves. The latter are generally ovate-rhombic, 7 to 12 cm (3 to 5 in) long by 5 to 20 cm (2 to 8 in) wide. ^[5]

The flower sits on a pedicel 2 to 6 cm (1 to 2.5 in) in length. The sepals are 15 to 50 mm (0.59 to 1.97 in) long and 6 to 20 mm (0.24 to 0.79 in) wide, while the petals are 15 to 70 mm (0.59 to 2.76 in) long and 10 to 40 mm (0.39 to 1.57 in) wide. Typically the flower opens white and becomes pink with age, but in the Smith River Canyon area of northern California and southern Oregon, the petals become almost barn-red. ^[13]

Taxonomy

In addition to Trillium ovatum Pursh, the following infraspecific taxa are accepted by Plants of the World Online: ^[14]

• Trillium ovatum var. oettingeri (Munz & Thorne) Case
• Trillium ovatum var. ovatum

Trillium ovatum var. oettingeri was first described as Trillium ovatum subsp. oettingeri by the American botanists Philip Alexander Munz and Robert Folger Thorne in 1973. ^{[15] [16]} The specific epithet honors Frederick W. Oettinger who collected the type specimen in July 1967. The type is one of about 1,500 specimens collected by Oettinger in the Marble Mountain Wilderness of the Salmon Mountains in western Siskiyou County, California. Hence Oettinger's trillium is also known as the Salmon Mountains wakerobin. ^[17]

Trillium ovatum var. oettingeri itself was treated by Frederick W. Case Jr. in Flora of North America in 2002. ^[18] Unlike the typical variety ovatum, variety oettingeri has leaves with short petioles and linear flower petals. ^{[19] [20]} More recently, the taxon was recommended at species rank based on morphological data and phylogenetic analysis. ^{[21] [22]}

Trillium ovatum f. maculosum Case & R.B.Case refers to a form with mottled leaves that occurs in Mendocino County, California. This is the only reported instance of mottled leaves in a pedicellate Trillium. ^{[23] [19]}

The names Trillium ovatum f. hibbersonii T.M.C.Taylor & Szczaw. and Trillium ovatum var. hibbersonii (T.M.C.Taylor & Szczaw.) G.W.Douglas & Pojar are synonyms for Trillium hibbersonii (T.M.C.Taylor & Szczaw.) D.O'Neill & S.B.Farmer, ^[24] a member of subgenus Trillium, the Trillium erectum group. Despite its provenance, Trillium hibbersonii is no longer thought to be related to Trillium ovatum. ^{[25] [26]}

Habitat and ecology

Trillium ovatum is often found growing in coniferous and mixed coniferous-deciduous forests, in and around alder thickets and shrubs. ^[23] Along the California coast, it is commonly found under coast redwood and mixed evergreen forest. ^[7] At Lolo Pass, Montana, it grows under spruce and Douglas fir in ravines along mountain streams. ^[27]

Flowers bloom late February in the southern part of its range, and in March or April elsewhere. Citizen science observations of flowering plants of this species peak during the first week of April. ^[28] For comparison, when Trillium grandiflorum is fully open in eastern North America, T. ovatum is already fading in western North America. Apparently T. ovatum lacks sufficient winter hardiness to flourish east of the continental divide. ^{[9] [29]}

The life-cycle stages of T. ovatum include a cotyledon stage, a one-leaf vegetative stage, a three-leaf vegetative (juvenile) stage, a three-leaf reproductive (flowering) stage, and a three-leaf nonflowering regressive stage. An example of the latter involves a transition from the three-leaf flowering stage to a three-leaf nonflowering regressive stage. Approximately one of every four reproductive plants regresses to a nonflowering state in any given year. ^[30] Under the right conditions, individuals may undergo extended dormancy, that is, they may cease above-ground growth for one or more years. In western Montana, dormancy was observed in all adult stage classes, with most plants returning to above ground status in a year or two, although some plants exhibited dormancy for 3–5 years. ^[31]

Conservation

In 2019, the global conservation status of Trillium ovatum was determined to be Secure (G5). ^{[1] [32]} At the same time, varieties Trillium ovatum var. oettingeri and var. ovatum were ranked Apparently Secure (T4) and Secure (T5), respectively. ^{[33] [34]} All known occurrences of variety oettingeri fall within protected areas in northern California but since the effects of wildfire and climate change are unknown, continued monitoring of existing populations is recommended. ^[35]

References

Bibliography

• Case, Frederick W.; Case, Roberta B. (1997). Trilliums. Portland, Oregon: Timber Press. ISBN  978-0-88192-374-2.
• O'Neill, Darlene M. (1995). Taxonomic study of Trillium ovatum forma hibbersonii (MS). University of British Columbia. Retrieved 20 February 2022.
• Pursh, Frederick (1814). Flora Americae Septentrionalis; or A systematic arrangement and description of the plants of North America. London. LCCN  05024608. Retrieved 8 September 2019.
• Ream, Tarn (2011). Life History and Demography of Trillium ovatum Pursh. (Liliaceae) in Western Montana (MIS). The University of Montana. Retrieved 2019-10-21.
• Wayman, Kjirsten A.; Wright, Alexander J.; Renner, Maralyn; Floden, Aaron; Lampley, Jayne A.; Farmer, Susan B.; Schilling, Edward E. (6 March 2024). "New insights into systematics of the Trillium ovatum complex". Madroño. 70 (3): 158–171. doi: 10.3120/0024-9637-70.3.158.

External links

• "Trillium ovatum". Jepson eFlora. The Jepson Herbarium. Retrieved 20 February 2022.
• "Trillium ovatum". Burke Herbarium Image Collection. Retrieved 20 February 2022.
• Trillium ovatum in the CalPhotos photo database, University of California, Berkeley
• Trillium and the Trillium family
• Pistrang, Mark. "Western White Trillium (Trillium ovatum var. ovatum)". United States Forest Service. Retrieved 7 October 2019.
• Dusek, Edith (Fall 1980). "Trilliums western style" (PDF). American Rock Garden Society Bulletin. 38 (4): 157–167. Retrieved 23 March 2022.
• Rottink, Bruce. "Trillium: The Princess of the Forest". Retrieved 17 September 2022.
• ""New" Trillium in Northwest California". Backcountry Press. Retrieved 2 April 2024.