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Trillium are Threatened with Extinction

Lovely three-petaled ephemeral spring plants can be found blooming in Michigan woodlands before deciduous trees are in full leaf. Trillium typically emerge in late April or early May in Northern Michigan. The blooms open slowly and may last into early June. When the blooms fade, the above-ground plants vanish, leaving only the underground plant structures to sleep until next year.

Trillium are extremely fragile, and picking the flowers seriously injures the plant by preventing it from producing food for the next year, often effectively killing the plant and ensuring none will grow in its place. Trillium typically thrives in moist, woodland settings where rich, acidic soil is present.

Most people are familiar with the larger white-flowering trillium (Trillium grandiflorum) which is common in our woods, but there are actually eight different species of trillium thought to occur naturally in our state. Four are rare and are assigned “Threatened” or “Endangered” protected status in Michigan. The state lists toadshade, prairie trillium, and snow trillium as threatened and painted trillium as endangered. A ninth species, green trillium, is believed to be extirpated, or disappeared completely from the state.

Protected trillium cannot be collected from the wild under any circumstances. However, trilliums are available from garden centers. These nursery plants can be treated just like any other perennial. They work well in a shade garden with woodland phlox (Phlox divaricate), false Solomon’s seal (Maianthemum racemosum), foamflower (Tiarella cordifolia), and ferns.

The status of trilliums in the wild was assessed in partnership with NatureServe, the New Mexico BioPark Society, and Mt. Cuba Center, the native plant garden and research facility in Delaware. Their report (published in April 2022) revealed that 32 percent of our native trillium species or varieties are threatened with extinction. The biggest concerns for the sustenance of trillium populations are animal grazing, urban development, and competition from invasive plants.

Repeated grazing from deer can eventually weaken plants and wipe out large areas. In regions where deer populations have increased, trilliums have nearly disappeared. When the blooms are removed, it means no seed will be set. The trillium reproduction cycle, from seed to flowering plant, takes four to seven years — a remarkably long time for herbaceous plants.

The invasives most likely to continue displacing trillium are Chinese privet (Ligustrum sinense), bush honeysuckle (Lonicera maackii) and garlic mustard (Alliaria petiolata). These plants form dense stands which impede the growth of native species.

Our club adopted the trillium as our logo several years ago. As Margaret Roach, the “In the Garden” columnist for the New York Times wrote last year, “Their distinctive, early flowers charm us, making them a kind of poster plant for other species in trouble, ambassadors for an interest in growing and conserving natives. Botanists often refer to them as ‘charismatic’ flora.” Hopefully, their charisma will capture you during a springtime walk in the woods.

For more information about trillium:

U.S. Forest Service: “About Trilliums”

Longfield Gardens: “All About Trillium”

Michigan Gardener: Plant Focus – Trillium

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