That good things come in threes was a lesson I learned in stages. It started years ago when I bought my house in the Hudson Valley and saw three small plants growing under the edge of the porch.
I didn’t know it then, but they were trilliums – specifically the native wake of the surrounding forests, also known as Trillium erectum. I lifted the anonymous creatures out with a trowel and moved them to a bed I was making, in case they were “something”.
They were indeed something. And now many of these short-lived spring plants bloom around my garden in May, all descended from those first three.
Most of the trillium knowledge I’ve gathered along the way felt tinged with serendipity or some sort of magic, like that first time. But not the latest installment, from a report published in April that analyzed risk factors for North American trillium in the wild.
The report revealed that 32 percent of our native trillium species or varieties are in danger of extinction, thanks to human development, predation by white-tailed deer and wild boar, competition from invasive plants and more.
The plight of any native species is cause for concern, but with trillium there is another layer — almost an emotional factor. Their distinctive early blooms charm us, making them a sort of poster plant for other struggling species, ambassadors for interest in growing and preserving native species. Botanists often call them “charismatic” flora.
Trillium speaks to people.
“Any organism that can stimulate the public — we need more of that,” said Wesley Knapp, chief botanist for NatureServe in Arlington, Virginia, one of three conservation nonprofit organizations behind “The Conservation Status of Trillium in North America” , the 86-page report. “We don’t have many of those kinds of communication tools.”
The status of trilliums in the wild was assessed in collaboration with the New Mexico BioPark Society and Mt. Cuba Center, the native botanical garden and research facility in Delaware. The genesis of the study: The medicinal group at the International Union for Conservation of Nature had funding to evaluate the condition of trillium, a genus used in traditional medicine. They approached the BioPark Society, who reached out to Mount Cuba, which in turn involved NatureServe, whose database, populated by member programs in the US and Canada, is a tool often used to assess plant status.
The three teams met with other North American experts for four days in October 2019, “to delve into maps, published information and personal observations from the field,” said Amy Highland, the director of collections and chief of conservation at Mt. . Cuba, which hosted the meeting.
The Latin phrase behind the idea that good things come in threes – omne trium perfectum – would have been invented for trillium.
As the plant’s prefix suggests, trillium parts come in threes: The flowers usually have three petals. Three sepals below the petals interlock to enclose the unopened bud. And what we call the leaves (technically bracts) usually occur in threes in mature plants as well.
Trillium counts about 50 species worldwide, most of them in North America. Their three areas of concentration — there’s that number again — are the eastern half of North America, the Pacific Northwest, and East Asia. The greatest diversity is in the American Southeast.
Structurally, trilliums fit into two primary groups. Some are petiolate – like my red and other northeastern varieties – holding their flowers above the leaves on a short peduncle or peduncle. Others are sessile, with the flowers sitting directly on the leaves. Leaves mottled with splashes of silver or purple are a hallmark of some sessile varieties, including several Southeastern ones, making them an additional choice to a gardener’s eye.
“Lush wildflowers with trillium as one element,” is how Mr. Knapp describes the spring shows in the cove forests of the Great Smoky Mountains. They can be companions such as blue cohosh (Caulophyllum thalictroides), columbine (Aquilegia canadensis), and broadleaf toothwort (Cardamine diphylla).
“In the eastern US, there are trillium species that live in the forest,” he said. “But the types of forests can be strikingly different, from rich inlet forests of the southern Appalachians to Atlantic coastal forests with more acidic, swampy soils.”
When botanizing, Mrs. Highland can find them with other species that can inspire shade-garden combinations, such as woodland phlox (Phlox divaricata), bloodroot (Sanguinaria canadensis), Virginia hyacinth (Mertensia virginica), or false Solomon’s seal (Maianthemum racemosum). In the gardens of Mount Cuba, clumps grow among ferns, foam flower (Tiarella cordifolia), wild ginger (Asarum canadense), and more.
Making more trillium: from ants and plants
I’ve watched the offspring of my trilliums expand their territory over the years, sprouting in the strangest of places and patterns. One group has almost lined up in a circle.
I apparently owe many generations of ants because they are participants in a form of mutualism between plants and animals called myrmecochory. Attracted to an elaiosome, a lipid-rich package attached to the trillium seed, the ant carries the whole thing back to its nest, feeds the elaiosome to its larvae, and then discards the seed.
This rich soil environment in and around ant nests is apparently favorable for the germination of trillium. Also, it is an advantage for a plant to have the seed set some distance from the parent: in case something happens to the original plant, there is a backup.
This form of seed dispersal is common among many native forest inhabitants, including violets, bloodroot, squirrel corn (Dicentra canadensis), and Dutch breeches (D. cucullaria). Ants may not be exactly gardeners: I now have trillium and other myrmecochore species growing in some very strange places because an ant decided to drop a seed there. But they are impressive ecosystem engineers.
“The first time I saw a trillium ring, I was very confused as a scientist,” said Mr. Knapp. “And then I saw it a few more times and learned what it was.”
“You feel like you’ve encountered some kind of fairy magic,” said Mrs. Highland. “Like, who put that circle there?”
If I intentionally move trilliums to a new spot, it’s not by seed, but by digging and dividing during the flowering period, when the plants are easy to see. I dig just outside the perimeter of a clump to lift it, then tease or cut apart the knobby underground rhizomes so that each division has at least one growing point.
Trilliums in trouble
The threats to trillium detailed in the report by Clayton Meredith, the New Mexico BioPark Society’s plant survival officer, also include human development. But predation from white-tailed deer and habitat damage from wild boars threaten more species of trillium than anything else.
As tough as the underground rhizomes of trilliums are, that toughness only goes so far in the face of repeated leafing by white-tailed deer. When the flowers are removed, it means that no seed will be set. Trillium’s reproductive cycle, from seed to flowering plant, takes four to seven years — a remarkably long time for herbaceous plants, Mr Knapp said — so a year lost is precious.
Wild boar rooting can destroy not only the plants they invert, but habitat as well. The animals — a hybrid of the Russian boars introduced to the south for hunting a century ago and domestic pigs that escaped farms — are gradually expanding their range, writes Mr. Meredith, moving north and west.
And then there are the competing plant species. The ones he names most likely to continue to displace trillium are Chinese privet (Ligustrum sinense), honeysuckle (Lonicera maackii), and garlic mustard (Alliaria petiolata), “each forming dense stands that hinder successive stages and directly affect herbaceous understory species.” Burning shrubs (Euonymus alatus), English ivy (Hedera helix), and Japanese stilt grass (Microstegium vimineum) are also on the list.
In the northwest, Himalayan blackberry (Rubus armeniacus) is the primary culprit of invasive plants. But the increasingly frequent wildfires there caused by climate change are also putting pressure on trillium populations.
A warehouse of genetics
Collecting wild plants for medicinal or horticultural purposes is another threat, but one that is more difficult to assess.
To avoid poaching, gardeners should only purchase plants that have been propagated in a nursery. Before buying, ask where the plants come from.
All of these factors emphasize the importance of ex situ, or off-site, conservation – such as the collection of 84 species of trillium that Mt. Cuba maintains, including genetic material “meant to live here until it’s needed again in the wild, when we can spread it and put it back,” said Ms. Highland.
The plight of trillium makes Mr. Knapp think about another group of charismatic plants, native orchids.
“When I started out, I remember seeing some wild orchids — a transformative moment for a young botanist,” he said. But by this time orchids were much less common than they had been just a generation earlier.
“Maybe I wasn’t that interested in it because I didn’t see hundreds of them on a site like 20 years before,” he said. “And now I keep thinking, won’t the next generation of botanists be enamored with trillium because they may never see masses of it?”
Margaret Roach is the creator of the website and podcast A way to gardenand a book of the same name.
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