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U.S. Forest Service


About Trilliums

Forty-three species of trillium are known worldwide with a startling thirty-eight represented in North America. Within the United States, the bulk of Trillium diversity is found in the eastern states where Terrific Trilliums are among the favorites on many a spring wildflower walk. Their blooms can be either showy or obscure, a dazzling display of color on a hillside, or a chance surprise hidden under a leaf. With their eye-catching flowers, it is hard to imagine anyone not enjoying the sight of a trillium along a trail on a fine spring morning!

Despite the visual simplicity of trilliums (they all have three petals and three sepals) they are actually a very complex group of plants that can confuse even the best of botanists. The many different species of trillium exhibit only a few and obscure structural differences, making separating the species difficult. One might think that the striking colors of the flowers might be a useful character for identification, yet many of the species have a variety of color forms, and it is not uncommon to find the two growing together! Additionally, many species hybridize, making identifications more difficult.

Trillium erectum Large clumps of red wake robins (Trillium erectum) adorn mesic slopes of the Appalachian Mountains in the spring. Trillium erectum also has a yellow form and a white form Photo by Mark Pistrang.

Trillium vaseyi Believe it or not, the stunning blooms of Vasey’s trillium (Trillium vaseyi) are often overlooked as they are found recurved under the large leaf-like bracts. Photo by Mark Pistrang.

Trillium luteum Yellow trillium (Trillium luteum) grace the side of a trail in the early spring. Photo by Mark Pistrang.

All trillium species belong to the Liliaceae (lily) family and are rhizomatous herbs with unbranched stems. Morphologically, trillium plants produce no true leaves or stems above ground. The “stem” is just an extension of the horizontal rhizome and produces tiny, scale like leaves (cataphylls). The above-ground plant is technically a flowering scape, and the leaf-like structures are bracts subtending the flower. Despite their morphological origins, the bracts have external and internal structure like a leaf, function in photosynthesis, and most authors refer to them as leaves.

Pedicellate and Sessile Trilliums

Trilliums are generally divided into two major groups: the pedicellate and sessile trilliums. In the pedicellate trilliums, the flower sits upon a pedicel that extends from the whorl of bracts, either “erect” above the bracts, or “nodding” recurved under the bracts. In the sessile trilliums there is no pedicel and the flowers appear to arise directly from the bracts. The photos below represent some of the diversity in each group.

Trillium simile Two distinct color forms of sweet white trillium (Trillium simile) occur side by side. Some white trilliums turn pink with age, but this rose-pink blossom was as fresh as its neighbor. The typical flower color for this species is white. Photo by Mark Pistrang.

Pedicellate Trillims

Trillium simile The large blossoms of sweet white trillium (Trillium simile) stand erect like sentries at the mouth of a small ephemeral stream. This species is a southern Appalachian endemic known only from a few counties in Georgia, North Carolina, and Tennessee. Photo by Mark Pistrang.

Trillium ovatum var. ovatum Known from the Pacific Northwest, south to California, and inland to Idaho, Montana, and Wyoming, the western white trillium (Trillium ovatum var. ovatum) is the most widespread representative in the western states. Photo by Tom Kogut.

Trillium vaseyi One of the so called “nodding” trilliums, Vasey’s trillium (Trillium vaseyi) is a local favorite on spring wildflower walks in the southeastern states. The pedicel is sharply recurved under the spreading bracts, often obscuring this floral treasure from direct view. Photo by Mark Pistrang.

Trillium catesbaei Most trilliums are found in rich moist habitats, but Catesby’s trillium (Trillium catesbaei) is a common species in the dry pine-oak forests of the southeastern states. Its pink petals and egg-yolk yellow anthers add a splash of color to the forest floor. Photo by Mark Pistrang.

Sessile Trilliums

Trillium cuneatum Trillium cuneatum is a common species in the southeastern states, however color morphs and subtle structural differences make it very difficult to separate from several other less common species. This sessile trillium is given the dubious common name of “toad shade” which really does nothing to describe its beauty! Photo by Mark Pistrang.

Trillium  luteum The yellow trillium (Trillium luteum) had long been considered a color morph of Trillium cuneatum, but more recent studies have shown it to be a distinct species. Both are southeastern species, but Trillium luteum is less common and has a smaller range, centered around east Tennessee. Photo by Mark Pistrang.

Trillium decumbens The decumbent trillium (Trillium decumbens) is very similar in appearance to the more common Trillium cuneatum with the exception that it seems to have no above ground “stem”. The rhizome of this species is often “s” shaped, arising from the ground several inches from where the bracts lay flat on the ground surface. Known only from a limited range in Alabama, Georgia, and Tennessee, this species often appears to have been “plucked” from its stem and laid on the ground along the side of a trail. Photo by Mark Pistrang.

Trillium ludovicianum The Louisiana trillium (Trillium ludovicianum) is another of the many trilliums that can be confused with Trillium cuneatum, separated primarily by petal width. Louisiana trillium is only known from Louisiana and Mississippi, but it overlaps and intergrades with Trillium cuneatum within the Mississippi portion of its range. Photo by Charles Allen.

Uses

Several species of Trillium contain chemical compounds called sapogenins that have been used medicinally though the ages as astringents, coagulants, expectorants, and uterine stimulants. This is evidenced in common names given to some trilliums such as birthwort and Indian balm.

For Future Generations

In addition to medicinal uses, like many of our native, showy wildflowers, trilliums are also subject to pressure from overzealous collectors and habitat loss due to land-use changes. If you desire to have trilliums in your garden, please visit a reputable nursery that propagates these species using ecologically sustainable methods.

Remember, collecting seed or any other plant material on the national forests and grasslands requires a permit. Please contact your nearest Forest Service office to request a permit before attempting to collect any native plant products. Native trilliums and their many derived hybrids and cultivars are readily available from the nursery trade and should not be collected in the wild.

Next: Lest They Disappear (rare trilliums)…

https://www.fs.usda.gov/wildflowers/beauty/trilliums/about.shtml