Pacific Northwest Native Plant Profile: Western trillium (Trillium ovatum)

Trillium ovatum

Although introductions are probably not necessary, this is Trillium ovatum, an unmistakable and endearing plant that softly lights up the vernal understory of moist coniferous and mixed forests from southern British Columbia, south to California, east to Idaho, Montana and small parts of Wyoming and Colorado, and north to southwestern Alberta. It’s part of a large genus, with about 50 other members that are native to temperate areas of North American and Asia.

T. ovatum’s common names are “western trillium” and “wake robin,” the latter due to its designation as unofficial (or maybe official!) harbinger of spring. Trillium comes from modern Latin, reportedly an alteration of the Swedish trilling, meaning “triplet,” which refers to its three leaves and three petals. Ovatum is derived from the Latin ovum meaning “egg-shaped,” which describes the leaf outline.

A perennial that grows from rhizomes, it technically produces no true leaves or stems above ground—the stems are considered an extension of the horizontal rhizome. The part of the plant that we notice most is an upright flowering scape (stalk), and the leaf-like structures are bracts, but most people call them leaves because they photosynthesize. The smaller leaf-like structures just under the flower are sepals. Probably more than you wanted to know! Trillium ovatum

Trillums are divided into two types: Pedicellate (those whose flowers have a short stalk called a peduncle) and sessile (those with flowers attached directly to the bracts). The flowers have six stamens and three stigmas. Trillium plants are very long lived and can take as long as 10 years to flower from seed. As the flowers age, and after pollination, the white flowers change to pink or even burgundy. Trillium are “spring ephemerals” and as summer proceeds, they go dormant and mostly disappear from our view (although with consistent water they will maintain their greenery above ground).

Wildlife value
Pollination happens thanks to bumblebees, moths, and beetles. The fruit is fleshy and berrylike; the seeds evolved to have fleshy elaiosomes, whose nutritious proteins and fats attract muscular ants who carry the seeds back home to feed their young. After the food is consumed, they then toss the still viable seed and, voila! Seed dispersal accomplished.

Try it at home
Although trilliums are quintessential forest denizens, they usually do well in shaded to partly shaded woodland gardens, or even just moist (but well drained) areas on the north or east side of houses, provided that the soil is rich in organic matter and slightly acidic (pH 5.0 to 6.5). Trilliums can withstand minor droughts, but occasional summer water will help keep them going until winter rains begin.

The plants you buy will likely be small, but in the right conditions and over many years they will slowly grow to a clump as wide as two feet. Grow them as nature would, in drifts with individual plants roughly a couple of feet apart. I’ve never grown them from seed, but reportedly seed is collected when capsules begin to open in midsummer. Sow them twice as deep as the seed’s diameter (or slightly deeper) in deep containers with coarse growing medium. Leave them outdoors in a shaded spot to mimic natural conditions. More detailed info on propagation here.

Some associates to grow them with include Douglas-fir, western red cedar, western hemlock, Pacific rhododendron, vine maple, salal, sword fern, deer fern, vanilla leaf, oxalis, western wild ginger, and stream violet.

Other Pacific Northwest trillium
Trillium albidum occurs in most parts of western Oregon, as well as Thurston, Pierce and Lewis counties in Washington, and much of northern California. T. parviflorum grows naturally in southwestern Washington and northwestern T. kurabyashiiOregon. T. rivale occurs only in southwestern Oregon and the northernmost counties of California. T. kurabayashii (pictured, right) is naturally found only in Oregon’s Curry County, as well as Del Norte and Humboldt counties of California.

As always, only buy natives from reputable nurseries and never dig plants from the wild. And never pick the flowers—doing so may eliminate the only chance the leaf-like bracts have for photosynthesis, and cause the plant to weaken or even die.

 

© 2017 Eileen M. Stark

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