This story was originally published on July 17, 2021.
This story is part of our series, Wild Pennsylvania. Check out all of the other stories in the series here.
Plant species are going extinct at alarming rates. Here in Pennsylvania, 349 native plant species are considered rare, threatened or endangered, according to the Pennsylvania Department of Conservation and Natural Resources. Last year, in response to the need for more on-the-ground conservation, DCNR established the Pennsylvania Plant Conservation Network. It works collaboratively with botanists, academics and volunteers on conservation projects.
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One plant they’re working to save is Canby’s mountain lover, scientific name Paxistima canbyi, one of the rarest plants in Pennsylvania. Only a couple dozen people have ever seen it growing in its habitat of limestone outcroppings in Appalachia.
“It’s not just rare in Pennsylvania, it’s globally rare,” says Steve Grund, botanist with the Pennsylvania Natural Heritage Program. Botanists believe that there are now fewer than 70 genetically distinct plants throughout its entire range, which extends from South Central Pennsylvania to Northern Tennessee.
Combating an Insect and an Invasive Vine
On a recent morning in June, Grund along with his colleague, botanist John Kunsman, and a few volunteers are in Bedford County, one of only three known sites in Pennsylvania, to try to save the plant from extinction. “It’s a really plausible outcome,” says Grund.
After Canby’s mountain lover was discovered in the backyard of the Chief Deputy for the Bedford County Sheriff’s Office, the Western Pennsylvania Conservancy bought the land – about 8 acres – in 1994, specifically to protect the plant. It’s also found in Shawnee State Park and on private land inaccessible to conservationists.
The mountain lover is threatened by quarries, erosion, fires and from being trampled by deer. But it’s biggest threat is an insect called Euonymus scale. It sucks nutrients from the plant, including water. Grund explains the insect is here because of an invasive vine called Oriental bittersweet, that serves as its host.
“It’s a terrible weed,” he says. “The fact that this Asian bittersweet is such a problem locally here and at this site is partly why the Canby’s mountain lover is in trouble here, because it has that scale.”
An amateur botanist named William Canby discovered the species on a bluff overlooking the New River in Virginia in 1858. It’s a short, shrubby evergreen plant that grows 8 to 10 inches tall, with little dark green leathery leaves. In May, it blooms with tiny white flowers and looks a little bit like rosemary.
The botanists grab their weapon for this mission — a highly-refined oil mixed with water and loaded-up in a squirt bottle. It suffocates the scale’s crawlers, the insect’s form after it hatches. Crawlers are the only stage of the scale that moves, and the only time in its life cycle that it’s vulnerable to the oil.
They walk several hundred yards uphill to a limestone cliff with about a 60 foot drop down. It looks like the sort of place you’d find rock climbers. The sun is dappled and the vegetation is lush. Pink flags are scattered around marking where the Canby’s mountain lover is growing.
Four times over the past three months, Grund and Kunsman, along with a few volunteers, have traveled to the site in Bedford County to spray and count the plant. Right now, the count is about the same as the one made in 2012, when the first treatment of the scale was done.
Grund gets down on the forest floor to get to work. He’s perched on the edge of the cliff. It’s slightly terrifying. He pulls on gloves to protect his hands, and then sprays the plant with the oil. Then he checks to see if there are any crawlers. He gets out a tiny bright yellow notebook to help.
“They’re very, very tiny,” he explains. “So what you do is you get a white piece of paper. My field notebook works fine for that. Put it under the plant, then you flick it with your fingers.”
If you’ve ever looked for spider mites on a house plant, it’s the same process.
Grund uses a magnifying glass he wears around his neck to examine the paper more closely. He doesn’t see any crawlers, which he says is a good sign.
“Maybe we timed it really well and got most of them last time,” he says.
Big Effort for One Small Plant
It’s a lot of effort for one small plant, but Grund says a team of stakeholders across the state – botanists, academics, DCNR, park rangers and active citizens – chose this plant to focus on because there’s action they can take.
“Often I feel like my job is to document the demise of rare plants,” Grund says. “But here we have a case where there’s something we can do about it, because there is a cause — that’s a scale insect — and there’s a treatment for it. We don’t know yet how successful we’ll be long term in treating it.”
“These things are all connected and sometimes we know what those connections are — often we don’t.”
The botanists believe that there’s a good chance that they can save the Pennsylvania populations of Canby’s mountain lover and keep it off the federal Endangered Species List, thanks to the DCNR funding of this treatment. Tat will save money in the long term.
When a plant is on the Endangered Species List, “the economy gets a lot more complicated when you’re talking about [environmental] impacts on development, roads, etc.” Grund explains.
So why should someone care that a small plant that only grows in three areas of the state might go extinct? One reason often used is that you never know what plant might contain the cure for cancer. Gund says it’s an argument botanists both love and hate, but it’s legitimate. However, Grund says it’s not just about what benefits humans, but the ecological connections, too.
“When you lose one species, then you might lose the species that feeds on it,” he says. “Then another species that that species feeds on might explode exponentially. You know, these things are all connected, and sometimes we know what those connections are — often we don’t.”
Botanists don’t know anything about Canby’s mountain lover’s role in its ecosystem. And they won’t have a chance if it disappears and just becomes something you’d find in a greenhouse, says Kunsman.
“We want to save this in its natural habitat, not in a botanical garden somewhere,” Kunsman says. “I want to see it growing where it should. That’s why we’re out here.”