Trillium Grandiflorum - Taxonomy

Taxonomy

Trillium grandiflorum was originally described as T. rhomboideum var. grandiflorum by André Michaux in his 1803 work Flora Boreali-Americana. T. rhomboideum is now a synonym of the closely related species T. erectum. T. grandiflorum was first treated as a species by Richard Anthony Salisbury only two years later. The species was traditionally placed in the subgenus Trillium, but recent work has shown the phylogeny of this grouping to be paraphyletic. Since then no phylogeny of the genus has garnered much agreement (The other subgenus, Phyllantherum, includes sessile-flowered species). T. grandiflorum is, alongside the western T. ovatum, one of the closer relatives to the subg. Phyllantherum members.

One form of the plant, T. grandiflorum f. roseum, opens with light pink petals instead of the common white. It is generally found very rarely throughout the range, but in the Blue Ridge Mountains of Virginia is can be found somewhat frequently in mixed or sometimes pure colonies. It should be noted that the white flowers of the common pure white variety of T. grandiflorum turn a very distinctive pink and remain so for several days just prior to the wilting of the flowers. Plants bearing these pink flowers are often mistaken for a "pink variety" of trillium.

Many variants of T. grandiflorum have green markings on the petals, as well as anywhere from 4 to 30 extra petals or bracts along with other highly deformed characteristics. Although many of these forms have been given taxonomic names, it has been shown that mycoplasma-like bacteria are responsible for the altered morphology in these individuals and not genetic variation. T. grandiflorum does, however, occasionally produce double-flowered forms such as T. g. f. polymerum. These are almost invariably sterile, but are much sought after for their appearance by trillium growers. It is the species of trillium that produces double flowers most frequently. On the other hand, and unlike other species such as T. erectum which hybridize fairly easily, T. grandiflorum is not known to form hybrids.