Trillium cernuum

Life-forms

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Monocots
Ordo: Liliales

Familia: Melanthiaceae
Tribus: Parideae
Genus: Trillium
Species: Trillium cernuum
Name

Trillium cernuum L., 1753
References

Linnaeus, C., 1753: Species Plantarum 1: 339

Vernacular names
English: Nodding trillium, nodding wakerobin, whip-poor-will flower
français: Trille penché

Trillium cernuum is a species of flowering plant in the bunchflower family Melanthiaceae. The specific epithet cernuum means "drooping, curving forwards, facing downwards",[3] a distinctive habit of its flower. It is commonly called nodding trillium or nodding wakerobin (not to be confused with Trillium flexipes) since the flower is invariably found nodding beneath the leaves.[4][5] It is sometimes referred to as the northern nodding trillium to distinguish from Trillium rugelii, a similar nodding species native to the southern Appalachian Mountains.[6] It is also called the whip-poor-will flower since presumably its bloom coincides with the spring arrival of the migrating bird with the same name.[7]

Trillium cernuum was thought to be one of three species of Trillium described by Swedish botanist Carl Linnaeus in 1753 (the other two being Trillium erectum and Trillium sessile). The specimen examined by Linnaeus was actually Trillium catesbaei, a nodding species native to the southern Appalachian Mountains where Trillium cernuum does not occur. This oversight led to much confusion, some of which continues to this day. Within its natural range, Trillium cernuum is often confused with two closely related Trillium species, Trillium erectum and Trillium flexipes. The three species are known to interbreed with one another, which adds to the confusion.

The nodding trillium is the most northerly Trillium species in North America, occurring as far north as Hudson Bay and as far south as northern Virginia. (Reports south of Virginia are most likely other species such as Trillium rugelii, Trillium catesbaei, or Trillium flexipes.) Trillium cernuum is found on rich, moist soils in both broadleaf and coniferous woodlands.

Description

Trillium cernuum is a perennial herbaceous plant that spreads by means of an underground rhizome. Up to three scapes (stems) rise directly from the rhizome, each standing 15–40 cm (6–16 in) tall. At the apex of the scape is a whorl of three leaf-like bracts, each 5–15 cm (2.0–5.9 in) long and 6–15 cm (2.4–5.9 in) wide.[4]

Flowering occurs from late April to early June, possibly as late as July in the northern part of its range.[8] A solitary flower hangs below the bracts (leaves) on a short recurved pedicel 1.5–3 cm (0.6–1.2 in) long. The flower has three slender pale green sepals, each 9–30 mm (0.4–1.2 in) long, and three strongly recurved white (rarely pink) petals, each 15–25 mm (0.6–1.0 in) long and 5–15 mm (0.2–0.6 in) wide. The flower is bisexual with six stamens and a single white (or pink) ovary shaped like a pyramid. Each stamen consists of a thin white filament and a pale lavender-pink (or gray) anther. The filaments and anthers are about the same length.[5][9]

If the flower is successfully pollinated, a single fruit develops. Initially the fruit is white (or pink), ripening to a dark red by late summer. When ripe, the fruit is a plump six-lobed berry up to 3 cm (1.2 in) in diameter.[4]
Trillium cernuum

A clump of nodding trillium, photographed in Minnesota on 17 May

A clump in Minnesota (17 May)
Nodding trillium with flower bud, photographed in Vermont on 14 May

With flower bud in Vermont (14 May)
Nodding trillium with flower, photographed in Ontario on 10 June

With flower in Ontario (10 June)
Nodding trillium with fruit, photographed in Vermont on 31 July

With fruit in Vermont (31 July)

Historically, Trillium cernuum has been confused with several nodding Trillium species native to the southern Appalachian Mountains. (See the Taxonomy section for more background information.) Within its natural range, T. cernuum is often confused with two sympatric Trillium species, T. erectum and T. flexipes. The following table compares these three species character by character while emphasizing the important characteristics of T. cernuum:

	T. erectum (red trillium)[10]	T. cernuum (nodding trillium)[4]	T. flexipes (drooping trillium)[11]
Stem	One or more per rhizome, clumps common; 1.5–6 dm (5.9–23.6 in) long	1–2(–3) per rhizome, each 1.5–4 dm (5.9–15.7 in) long	One or more per rhizome, each 2–5 dm (7.9–19.7 in) long
Leaves	Sessile, rhombic to ovate-rhombic; 5–20 cm (2.0–7.9 in) long and wide, widest near the middle	Sessile or subsessile with narrow leaf bases; 5–15 cm (2.0–5.9 in) long and 6–15 cm (2.4–5.9 in) wide	Sessile, rhombic; 15–25 mm (0.6–1.0 in) long and wide, often wider than long
Pedicel	Various habits but not recurved below the leaves; 1–10 cm (0.4–3.9 in) long	Short and strongly recurved below the leaves; 1.5–3 cm (0.6–1.2 in) long	Various habits but rarely recurved below the leaves; 4–12 cm (1.6–4.7 in) long
Flower	Usually faces downward; smells like a wet dog	Nodding below the leaves	Erect forms face outward
Sepals	Green, often streaked with maroon; 10–50 mm (0.4–2.0 in) long	Green; 9–30 mm (0.4–1.2 in) long	Green, weakly recurved; 14–45 mm (0.6–1.8 in) long
Petals	Dark reddish brown, maroon, purple, or white; heavily textured; 15–50 mm (0.6–2.0 in) long and 10–30 mm (0.4–1.2 in) wide	White (rarely pink), strongly recurved; thin textured; 15–25 mm (0.6–1.0 in) long and 9–15 mm (0.4–0.6 in) wide	Creamy white, dark reddish brown, or maroon; heavily textured; 20–50 mm (0.8–2.0 in) long and 10–40 mm (0.4–1.6 in) wide
Stamens	Anthers dark maroon, gray-maroon, or yellow with pollen; filaments as long as (or longer) than the anthers	Anthers pale lavender-pink or gray; filaments and anthers approximately equal in length	Anthers thick, creamy white or yellow; anthers at least twice as long as the filaments
Ovary	Dark purple or maroon; ovoid to spherical; strongly ridged	White or pink flushed; flask-shaped; ridged	White or pink flushed; flask-shaped; strongly ridged
Fruit	(same as ovary)	White or pink initially, but ripens to dark red; ridges become angles as the fruit expands	White or pink initially, but ripens to rosy red or purplish; strongly angled

Identification typically requires a mature, flowering plant. When not in flower, the three species are difficult to distinguish. Moreover, the three species are known to interbreed with one another, which can add to the confusion.

To distinguish among T. cernuum, T. erectum, and T. flexipes, start by examining the pedicel. If the pedicel is longer than 3 cm (1.2 in), it is not T. cernuum. More importantly, the pedicel of T. cernuum is strongly recurved below the leaves while the other two species rarely exhibit this behavior.

Northern forms of T. flexipes tend to have recurved pedicels and/or recurved petals. These forms closely resemble large plants of T. cernuum and so the two are often confused. In such cases, examine the stamens. The anthers of T. cernuum are slender, lavender-pink or purplish, with the anthers and filaments approximately equal in length, while the anthers of T. flexipes are thick, creamy white or yellow, with the anthers greatly exceeding the length of the usually very short filaments.[12]
Taxonomy

Trillium cernuum was first thought to be described by Carl Linnaeus in 1753.[13] Linnaeus gave the location of his type specimen as "Carolina," however, T. cernuum does not range that far south. The resulting confusion surrounding the pedicellate-flowered Trillium species persisted for 150 years. In 1906, Gleason shed some light on the confusion by showing how to distinguish T. cernuum from T. flexipes on the basis of anther-filament ratio. However, Gleason mistakenly believed that the range of T. cernuum extended south to Georgia.[14] Finally, in 1938, Barksdale showed conclusively that the specimen described by Linnaeus was actually T. catesbaei and that T. cernuum is absent from the southern Appalachian Mountains.[15]

As of September 2021, Plants of the World Online (POWO) lists 14 synonyms for T. cernuum.[2] Although POWO accepts no infraspecific names, numerous varieties and forms have been described. For example, Eames and Wiegand described T. cernuum var. macranthum in 1923.[16] The typical variety, found along the North American coast from Delaware to Newfoundland, is described as a small delicate plant, while variety macranthum, found elsewhere, is claimed to be larger and more robust. Although there may be regional size trends, much of the variation in size is largely dependent upon soil nutrients, and so the variety is not generally accepted by botanists.[4][17]

Edgar T. Wherry (1885-1982) described Trillium cernuum f. tangerae in 1945.[18] With deep rose-colored petals, the form is thought to be a hybrid with T. erectum.[17]
Distribution

The range of Trillium cernuum extends across Canada, from Saskatchewan in the west to Newfoundland in the east, and as far south as northern Virginia in the mid-Atlantic United States. The species is known to occur in the following provinces, states, and territories:[2][4][19]

Canada: Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan
United States:[20] Connecticut, Delaware, District of Columbia, Illinois, Indiana, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, Virginia, West Virginia, Wisconsin
Other: Saint Pierre and Miquelon

At the southern end of its range, T. cernuum grows in rich, cool, moist to swampy deciduous woods, and along shrubby stream banks and pond edges of deep forests. In Michigan, it also occurs along streams and swamps, but in conifer-hardwood forests. In its northern range, it occurs in dryer (although still moist), upland deciduous-coniferous woods.[1]

As of October 2019, T. cernuum is globally secure.[1] It is vulnerable (or worse) in at least a dozen states and provinces. In particular, it is critically imperiled in Illinois, Indiana, and West Virginia.[21][22][23] In Lake County, Ohio, a single specimen was collected in 1879, but T. cernuum is now thought to be extirpated from Ohio.[24]
Bibliography

Barksdale, Lane (1938). "The pedicellate species of Trillium found in the southern Appalachians". Journal of the Elisha Mitchell Scientific Society. 54 (2): 271–296. JSTOR 24332541.
Case, Frederick W.; Case, Roberta B. (1997). Trilliums. Portland, Oregon: Timber Press. pp. 88–92. ISBN 978-0-88192-374-2.

References

"Trillium cernuum". NatureServe Explorer. NatureServe, Arlington, Virginia. Retrieved 27 September 2021.
"Trillium cernuum L.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 27 September 2021.
Gledhill, David (2008). The Names of Plants (4th ed.). Cambridge University Press. p. 100. ISBN 978-0-521-86645-3.
Case Jr., Frederick W. (2002). "Trillium cernuum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 26. New York and Oxford. Retrieved September 24, 2007 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
"Trillium cernuum". Northern Ontario Plant Database. Retrieved September 24, 2007.
Stritch, Larry. "Northern Nodding Trillium (Trillium cernuum)". United States Forest Service. Retrieved 1 July 2019.
"Nodding Trillium, Trillium cernuum L.". Eloise Butler Wildflower Garden. Retrieved 20 October 2021.
Case & Case (1997), p. 90.
Case & Case (1997), pp. 89–90.
Case Jr., Frederick W. (2002). "Trillium erectum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 26. New York and Oxford. Retrieved September 24, 2007 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Case Jr., Frederick W. (2002). "Trillium flexipes". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 26. New York and Oxford. Retrieved September 24, 2007 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Case & Case (1997), p. 103.
"Trillium cernuum L.". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew. 2021-10-02. Retrieved 2021-10-02.
Gleason, Henry Allan (July 1906). "The pedunculate species of Trillium". Bulletin of the Torrey Botanical Club. 33 (7): 387–396. Retrieved 24 October 2021.
Barksdale (1938), pp. 271–273.
Eames, A.J.; Wiegand, K.M. (November 1923). "Variations in Trillium cernuum". Rhodora. 25 (299): 189–191. Retrieved 27 September 2021.
Case & Case (1997), p. 91.
"Trillium cernuum f. tangerae Wherry". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew. 2021-10-18. Retrieved 2021-10-18.
"Trillium cernuum". State-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved 27 September 2021.
"Trillium cernuum". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved 27 September 2021.
Mankowski, Anne, ed. (February 2011). "Endangered and Threatened Species of Illinois: Status and Distribution" (PDF). Volume 4: 2009 and 2010 Changes to the Illinois List of Endangered and Threatened Species. Illinois Endangered Species Protection Board. Retrieved 27 September 2021.
"Endangered, Threatened, Watch List and Extirpated Plants of Indiana" (PDF). Indiana Department of Natural Resources. 14 May 2021. Retrieved 28 September 2021.
"Rare Plants tracked by the West Virginia Natural Heritage Program" (PDF). West Virginia Division of Natural Resources. 4 August 2020. Retrieved 28 September 2021.
"Rare Plants of Ohio". ODNR Division of Natural Areas and Preserves. Retrieved 4 September 2019.