Trillium

February 2022 | EDUCATION

Want to learn more about some of the plants found in the Allegheny Plateau? Read below to learn about Trillium, a fascinating genus with multitudes of species you may have seen throughout our ecoregion, North America, and Asia.

History

In 1753, Swedish botanist Carolus Linnaeus established the genus Trillium by recognizing three species: Trillium cernuum, Trillium erectum, and Trillium sessile. For centuries, the placement of the Trillium genus has been wrangled between one family or another, separated or lumped together with other genera. Trillium can be separated into four major lineages: Erectum group (15 species), Grandiflorum group (3 species), Trillium L. Subg. Delostylium Raf. (5 species), and Trillium L. subg. Sessilium Raf. (26 species).

Trillium, wakerobin, toadshade, tri-flower, birthroot, birthwort, and sometimes wood lily are all common names for a genus of roughly 50 species in the Bunchflower Family (Melanthiaceae). They are perennial, herbaceous flowering plants growing from rhizomes, native to temperate regions of North America and Asia.

Perennial – A plant that lives for 3+ years and overwinters outside.
Herbaceous – Fleshy, not woody.
Rhizomes – A fleshy, horizontal underground stem which puts out lateral shoots and adventitious roots at intervals.
Temperate – The area or region between the Tropic of Cancer and the Arctic Circle in the Northern Hemisphere.

The greatest variety of species is found in the southern Appalachian mountains of the United States. Trillium features three large, leaf-like bracts arranged in a whorl around a scape rising directly from the rhizome. 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. Fruit is fleshy and capsule-like, or berry-like. The seeds have large, oily elaiosomes.

Trillium in North America

Canada – Trillium species are found from Newfoundland to southern British Columbia. The greatest diversity of species are found in Ontario, Quebec, and Nova Scotia.

United States – Species are found throughout the contiguous US, excluding desert regions of the Southwest. In the West, species are found from Washington to central California, and east to the Rocky Mountains. In the East, species range from Maine all the way to northern Florida, and west to the Mississippi River Valley. Trillium species are especially diverse in Georgia, Tennessee, Alabama, North Carolina, and South Carolina. There are 21 different species found in the state of Georgia alone.

Trillium in Asia

In Asia, the range of species extends from the Himalayan Mountains, across China, Korea, eastern Russia, and Japan, all the way to the Kuril Islands. The greatest diversity of Trillium species is found on the islands of Japan and Sakhalin.

Trillium at Pittsburgh Botanic Garden

Trillium thrives in partially-shaded, deciduous woodland conditions that are high in organic matter. These conditions may be found in the Allegheny Plateau Woodland. Trillium is present at Pittsburgh Botanic Garden, but may only be visible during certain times and weather conditions.

Trillium, Insects & Animals

Ants – Each seed of a ripe fruit has a fleshy appendage called an elaiosome. Ants are attracted to Trillium’s elaiosomes, and often bore holes into the fruit to avoid waiting for it to drop off on its own. The ants then carry the seeds back to their nesting place, eat the elaiosome, then discard the seeds. These seeds eventually germinate, an average of about 1 meter away from the original parent plant.

Yellow Jackets & Wasps – Yellow jackets (Vespula spp.) and other wasps are also attracted to these elaiosomes. These wasps carry, feed on, and disperse seeds in a similar manner to ants, an average of 1.4 meters away from the parent plant. Yellow jackets are documented seed dispersers for at least three species of Trillium (T. catesbaei, T. cuneatum, T. undulatum).

Conditions & Conservation

Light – Trillium grows best in a partly-shaded, deciduous woodland habitat and along wet areas in the forest. Further South, they will require more shade.

Soil – Trillium grow well in fertile, moist, but well-drained soil that is high in organic matter.

Conservation – Picking parts off of these plants can kill them, even if the rhizome is undisturbed. Some species are listed as threatened or endangered, and collecting these species may be illegal. In Michigan and Minnesota, it is illegal to pick Trilliums. In New York, it is illegal to pick the red trillium. The rare drooping trillium (Trillium flexipes) is also protected by law in Ontario, due to its decreasing Canadian population.

Did You Know?

The white trillium (Trillium grandiflorum) serves as the official flower and emblem of the Canadian province of Ontario, as well as the official wildflower of the State of Ohio.

In light of this shared connection, Major League Soccer teams Columbus Crew and Toronto FC compete annually for the “Trillium Cup.”

There are numerous Trillium Festivals each year, including events in Oregon, Ohio, and Virginia.

In Mexico, Trillium is used as an icon on certain flags to recognize LGBTQ pride.

– By Dr. Mark Miller, Education & Exhibits Director