Trillium (trillium, wakerobin, toadshade, tri flower, birthroot, birthwort, and sometimes "wood lily") is a genus of about fifty flowering plant species in the family Melanthiaceae. Trillium species are native to temperate regions of North America and Asia, with the greatest diversity of species found in the southern Appalachian Mountains in the southeastern United States.
Description
Plants of this genus are perennial herbs growing from rhizomes. There are three large leaf-like bracts arranged in a whorl about a scape that rises directly from the rhizome. There are no true aboveground leaves but sometimes there are scale-like leaves on the underground rhizome. The bracts are photosynthetic and are sometimes called leaves. The inflorescence is a single flower with three green or reddish sepals and three petals in shades of red, purple, pink, white, yellow, or green. At the center of the flower there are six stamens and three stigmas borne on a very short style, if any. The fruit is fleshy and capsule-like or berrylike. The seeds have large, oily elaiosomes.
Occasionally individuals have four-fold symmetry, with four bracts (leaves), four sepals, and four petals in the blossom.Kevin Kirkland, Two 4-petaled trilliums found, Pittsburgh Post-Gazette, 11 May 2013; Trillium erectum and Trillium grandiflorum examples are given.. The tetramerous condition has been described for several species of Trillium including T. chloropetalum, T. erectum, T. grandiflorum, T. maculatum, T. sessile, and T. undulatum.
Taxonomy
In 1753, Swedish botanist Carl Linnaeus established the genus Trillium by recognizing three species, Trillium cernuum, Trillium erectum, and Trillium sessile. The type specimen Trillium cernuum described by Linnaeus was actually Trillium catesbaei, an oversight that subsequently led to much confusion regarding the type species of this genus.
Initially the Trillium genus was placed in the family Liliaceae. In the nineteenth and early twentieth centuries it was sometimes placed in a smaller family, Trilliaceae. By 1981 Liliaceae had grown to about 280 genera and 4,000 species. As it became clearer that the very large version of Liliaceae was polyphyletic, some botanists preferred to place Trillium and related genera into that separate family. Others defined a larger family, Melanthiaceae, for a similar purpose, but included several other genera not historically recognized as close relatives of Trillium. This latter approach was followed in 1998 by the Angiosperm Phylogeny Group, which assigned the genus Trillium, along with its close relative Paris, to the family Melanthiaceae. However, other taxonomists have since preferred to break up the heterogenous Melanthiaceae into several smaller monophyletic families, each with more coherent morphological features, returning Trillium to a resurrected Trilliaceae.
In 1850, German botanist Carl Sigismund Kunth segregated Trillium govanianum into genus Trillidium. Some authorities consider Trillidium to be a synonym for Trillium , while others recognize the taxon Trillidium govanianum based on morphological differences (with other Trillium species) and molecular evidence. Still others support the segregation of Trillium undulatum into genus Trillidium alongside Trillidium govanianum.
Subdivisions All names used in this section are taken from the International Plant Names Index. , Plants of the World Online (POWO) accepts 49 species and 5 named hybrids, all of which are listed below. The geographical locations are taken from POWO and the Flora of North America, except where noted.
The Trillium genus has traditionally been divided into two subgenera, Trillium subgenus Trillium and Trillium subgenus Phyllantherum, based on whether the flower is pedicellate or sessile. At the time, the former subgenus was considered to be the more primitive group. Based on molecular systematics, Trillium subgen. Phyllantherum has been shown to be a monophyletic group, but its segregation renders the remaining Trillium subgen. Trillium paraphyletic.
Trillium subgenus Phyllantherum was named by Constantine Samuel Rafinesque in 1820, but since he did not provide a description, the name was declared invalid in 2014. At that time, the correct name was thought to be Trillium subgen. Sessilium, which was described by Rafinesque in 1830. However, that name was later found to be incorrect as well. , the correct name of the subgenus is Trillium subgen. Sessilia Its type species is Trillium sessile
In 1819, Rafinesque described and named the genus Delostylis, and then placed Trillium stylosum (now a synonym for Trillium catesbaei ) into the new genus. Reversing himself a decade later, Rafinesque instead placed Trillium stylosum into a new subgenus Delostylium in 1830. Presumably Rafinesque had intended the subgeneric name to replace the earlier generic name, and so the correct name of the former is Trillium subgen. Delostylis . Its type species is Trillium catesbaei. Historically, the subgenus has been known as the Catesbaei group. The word Delostylis means "with a small but conspicuous style".
Based on morphology and molecular evidence, a few taxa in genus Trillium have been segregated into other genera:
Trillium rivale, first described in 1885, was segregated into genus Pseudotrillium in 2002. The name Pseudotrillium rivale is widely recognized. Trillium govanianum, first described in 1839, was segregated into genus Trillidium in 1850. However, the name Trillidium govanianum is not widely recognized. Trillium undulatum, first described in 1801, was segregated into genus Trillidium in 2018, but the name Trillidium undulatum is controversial and not widely recognized.
Phylogenetic analysis places Trillidium govanianum and Trillidium undulatum together in a clade with high support. However, since Trillium and Trillidium are both individually and collectively monophyletic, it is a matter of choice whether or not to recognize genus Trillidium.
Excluding the segregate taxa listed above, the remaining taxa separate into four clades with the following names:
Trillium subgen. Trillium Trillium subgen. Callipetalon Trillium subgen. Delostylis [as Delostylium] Trillium subgen. Sessilia [as Sessilium]
Traditionally, Trillium subgen. Trillium has included all pedicellate-flowered species (which is a paraphyletic group), but in 2022, the subgenus was circumscribed as a clade of fourteen (14) species. Its type species is Trillium erectum Historically, the subgenus has been known as the Erectum group.
Trillium subgen. Callipetalon was described by Jayne A. Lampley and Edward E. Schilling in 2022. The word Callipetalon means "beautiful petal", a reference to "the famously beautiful flowers" of its type species, Trillium grandiflorum Historically, the subgenus has been known as the Grandiflorum group.
This leads to a four-part concept of Trillium that sharply contrasts with the traditional pedicellate vs. sessile dichotomy outlined previously.
Subgenus Trillium Trillium subgen. Trillium, the Erectum group, is a group of pedicellate-flowered trilliums that includes Trillium erectum. The subgenus was circumscribed as a clade of fourteen (14) species in 2022. Species in this subgenus have pedicellate flowers (on a stalk) with three distinct stigmas (no style) and solid green leaves (not mottled). They are distributed across North America and Asia. Hybrids are common within this subgenus (the only group of pedicellate-flowered trilliums with natural hybrids).
Trillium apetalon – Japan, Kuril Islands, E Russia (Sakhalin) Trillium camschatcense – NE China (Jilin), Japan, Korea, Kuril Islands, E Russia (Primorsky Krai, Khabarovsk Krai, Kamchatka Peninsula, Sakhalin) Trillium cernuum – Manitoba, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan; Connecticut, Delaware, 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; Saint Pierre and Miquelon Trillium channellii – Japan (E Hokkaido) Trillium erectum – New Brunswick, Nova Scotia, Ontario, Quebec; Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, West Virginia Trillium flexipes – Ontario; Alabama, Arkansas, Delaware, Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, South Dakota, Tennessee, Virginia, West Virginia, Wisconsin Trillium × hagae (Trillium camschatcense × Trillium tschonoskii) – Japan, E Russia (S Sakhalin) Trillium hibbersonii – British Columbia Trillium × komarovii (Trillium camschatcense × unknown) – Japan, E Russia (Primorsky Krai) Trillium × miyabeanum (Trillium apetalon × Trillium tschonoskii) – Japan Trillium rugelii – Alabama, Georgia, North Carolina, South Carolina, Tennessee Trillium simile – Georgia, North Carolina, Tennessee Trillium smallii – Japan, E Russia (S Sakhalin) Trillium sulcatum – Alabama, Georgia, Kentucky, North Carolina, Tennessee, Virginia, West Virginia Trillium taiwanense – E Taiwan Trillium tschonoskii – Bhutan, China (Anhui, Fujian, Gansu, Hubei, Shaanxi, Sichuan, Tibet Autonomous Region, Yunnan, Zhejiang), NE India (Sikkim), Japan, Korea, Kuril Islands, Myanmar, Russia (Sakhalin), Taiwan Trillium vaseyi – Alabama, Georgia, North Carolina, South Carolina, Tennessee Trillium × yezoense (Trillium apetalon × Trillium camschatcense) – Japan
Subgenus Callipetalon Trillium subgen. Callipetalon, the Grandiflorum group, is a group of pedicellate-flowered trilliums that includes Trillium grandiflorum. The subgenus was circumscribed as a clade of three (3) species in 2022. Species in the subgenus have pedicellate flowers (on a stalk) and solid green leaves (except T. ovatum on the west coast of California, which occasionally has mottled leaves). The stigmas are fused together at their bases (basally connate) but lack a definite style. They are distributed across North America (but not Asia). Flowers were and still are consumed and used by indigenous peoples in various regions of North America.
Trillium crassifolium – Washington Trillium grandiflorum – Nova Scotia, Ontario, Quebec; Alabama, Connecticut, Delaware, District of Columbia, Georgia, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, West Virginia, Wisconsin Trillium nivale – Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, Nebraska, Ohio, Pennsylvania, South Dakota, West Virginia, Wisconsin Trillium ovatum – Alberta, British Columbia; California, Colorado, Idaho, Montana, Oregon, Washington, Wyoming Trillium scouleri – Alberta, British Columbia; Colorado, Idaho, Montana, Washington, Wyoming
Subgenus Delostylis Trillium subgen. Delostylis, the Catesbaei group, is a group of pedicellate-flowered trilliums that includes Trillium catesbaei. The subgenus was circumscribed as a clade of seven (7) species in 2022. Species in this subgenus have pedicellate flowers (except for one variety of T. pusillum) with a definite style and solid green leaves (not mottled). Distribution is restricted to the southeastern and south central United States.
Trillium catesbaei – Alabama, Georgia, North Carolina, South Carolina, Tennessee Trillium georgianum – Georgia Trillium persistens – Georgia, South Carolina Trillium pusillum – Alabama, Arkansas, Kentucky, Maryland, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Virginia, West Virginia Trillium texanum – Arkansas, Louisiana, Texas
Subgenus Sessilia