by Dr. Stanley Temple

Among the early blooming wildflowers that announce the awakening spring season, few rival trilliums. Trillium grandiflorum—also known as the white trillium, great white trillium, large-flowered trillium, or the white wake-robin—is a legendary reminder that life is returning after the hardships of winter. Their large clonal colonies can form spectacular “carpets” of flowers in rich woodlands. Many Native American tribes regard trillium as a sacred plant; its three petals are associated with the Christian concept of the Trinity; it is used in traditional medicine as the “birthroot;” its sensitivity to environmental disturbances make it a useful indicator species; and its declining populations and slow recovery from disturbance make it a conservation target. So, when PBS Wisconsin wanted to interview me for a feature about spring phenology, I was not surprised they wanted to film me with a large patch of trillium in the background.

The film crew asked me to locate a photogenic carpet of these stunning spring ephemerals for the interview. No problem, I thought. Back in the 1970s, when my students and I were censusing birds in woodlands across southern Wisconsin, we frequently encountered dense drifts of white blossoms on the forest floor. I asked for a week’s lead time to find the right setting, and I started my quest by revisiting places where I remembered carpets of trilliums.

Those lush blankets of flowers that I remembered were no more.

I asked fellow naturalists for tips on other places. Some of the locations they recommended are formally protected for their conservation values. I even looked at sightings reported by citizen scientists on iNaturalist—but what initially appeared to be a large patch of trilliums on the online maps was actually a small number of plants reported repeatedly by a large number of observers.

The date of the interview was approaching. Yet each of the sites I visited either no longer had any trilliums or had only scattered plants but no large colonies. Some of the formerly healthy woods no longer even existed, having been heavily logged or razed entirely to construct new developments. Other sites had been overtaken by invasive plants like garlic mustard that outcompeted the trilliums. And all of the sites showed evidence of heavy browsing by white-tailed deer. Trilliums, especially large-flowered trilliums, are highly palatable to deer. The recent overabundance of white-tailed deer on the southern Wisconsin landscape meant that few trillium colonies had escaped being browsed.

Every site was a poignant echo of Aldo Leopold’s lament: “One of the penalties of an ecological education is that one lives alone in a world of wounds.”

Low on my dwindling list of potential sites was a small, wooded city park surrounded by urban development on the east side of Madison. When I finally visited Heritage Sanctuary, I was both relieved and surprised. This 9.3-acre patch of forest had several colonies of trillium and other spring ephemerals. The surrounding housing developments had effectively formed a barrier that prevented deer from reaching the site, and there was evidence of ongoing control of invasive plants as well. The interview was a success, but another example of living in a “world of wounds” had been revealed. There are few places left in southern Wisconsin that have escaped the impacts of an overabundant deer population.

By chance, the week following the PBS interview I was the keynote speaker for the annual Trillium Festival at Maiden Rock in northwestern Wisconsin. In view of my disappointing experience in the southern part of the state, I wondered if there would even be any trilliums left to celebrate. I was delighted to find the steep hillsides of the Mississippi River coulees carpeted in flowers. Growing in an area difficult for deer to traverse, the trilliums there had escaped browsing—but it again made the reality painfully clear. Wherever deer can go, trilliums decline or disappear.

Aldo Leopold wrote eloquently about his personal experience with out-of-control deer populations in his essay “Thinking Like a Mountain.” In 1942, while he was serving as a Conservation Commissioner and setting Wisconsin’s conservation priorities, that experience became a public warning of the “wounds” overabundant deer populations could inflict on local ecosystems. Leopold recognized that the state’s deer herd was entering an accelerated phase of population growth that, if not halted, would eventually lead to difficult-to-reverse overabundance and predictable ecological damage. To slow the rate of growth, he advocated the first-ever harvest of antlerless deer during the hunt of 1943. Shooting antlerless deer, a normal deer management strategy today, was considered heresy back then. And in a classic example of unfortunate timing, Leopold became the object of ad hominem attacks triggered in part by emotional reactions to the 1942 movie “Bambi.” Public opposition was swift, and he was pilloried as the “Bambi killer.”

As top predators like wolves were eliminated and human hunters became the main predators of deer, the intensity of our hunting pressure needed to become sufficient to counter deer’s rate of population growth in a modern environment that favors them. But past cultural norms like hunting only bucks, management decisions that tacitly allowed population growth to continue, and declining interest in hunting meant that the annual deer harvest has largely failed to keep up since Leopold’s time.

Leopold’s prescient insights remain relevant in discussions about wildlife management and conservation today. Just as he predicted, deer populations in Wisconsin are proving difficult or impossible to bring into ecological balance. One study posits that 12 deer per square mile is the maximum density compatible with thriving trillium populations; however, Wisconsin currently averages about 35 deer per square mile, with much higher densities in many areas. As deer populations have increased, ecological impacts of their browsing have mounted, threatening the health of woodland ecosystems. Trillium is sadly just one casualty among the many.

How many more carpets of trillium in spring woods will be lost before we recognize and work to heal the “wounds” inflicted by overabundant deer?

Learn more about the history and impacts of deer overpopulation.