Trillium

''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.. 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 closest relatives, ''Paris'' and '' Pseudotrillium'', 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''.

Infrageneric taxa

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.

Subgenera

The ''Trillium'' genus has traditionally been divided into two subgenera, ''Trillium'' subgenus ''Trillium'' and ''Trillium'' subgenus ''Sessilium'', based on whether the flowers are pedicellate or sessile with respect to their attachment to the apex of the scape. The former is considered the more primitive group. Until recently the sessile-flowered subgenus was known by the name ''Phyllantherum'', but the name ''Sessilium'' has precedence and should be used instead. has been shown to be a monophyletic group by molecular systematics but its segregation renders the remaining paraphyletic.

In 1830, Rafinesque placed ''Trillium catesbaei'' into subgenus ''Delostylium''. Since then ''Trillium persistens'' and all members of the ''Trillium pusillum'' species complex (including ''Trillium georgianum'' and '' Trillium texanum'') have been added to this subgenus, which has been shown to be monophyletic. Members of  are distinguished from other pedicellate-flowered trilliums by the presence of a definite style. The word ''Delostylium'' means "with a small but conspicuous style".

Phylogenetic analysis confirms the monophyly of ''Trillidium'' and supports the inclusion of ''Trillium undulatum'' into that genus. Excluding ''Trillium govanianum'' and ''Trillium undulatum'' from the analysis, genus ''Trillium'' can be separated into four major lineages:

# Erectum group (15 species)
# Grandiflorum group (3 species)
# ''Trillium''
# ''Trillium''

Since all four species groups are monophyletic, this leads to a four-part concept of ''Trillium'' that sharply contrasts with the traditional pedicellate vs. sessile dichotomy outlined previously.

Erectum group

This group of species has pedicellate flowers (on a short stalk) with three separate stigmas (no style) and solid green leaves (not mottled). Species in this group are distributed across North America and Asia, as indicated below. Hybrids are common within this group (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

Grandiflorum group

This group of species has pedicellate flowers (on a short 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. Species in this group are distributed across North America (but not Asia). These flowers were and still are consumed and used by Native Americans in different regions of 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

''Trillium'' subgenus ''Delostylium''

This subgenus has 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, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia

''Trillium'' subgenus ''Sessilium''

This subgenus (previously known as ) includes species with sessile flowers (no flower stalk), erect petals (except in ''T. stamineum''), and mottled leaves (except in ''T. petiolatum'' and occasionally in plants of other sessile-flowered species).

* ''Trillium albidum'' – California, Oregon, Washington
* ''Trillium angustipetalum'' – California
* ''Trillium chloropetalum'' – California
* ''Trillium cuneatum'' – Alabama, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee
* ''Trillium decipiens

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