Every year in early summer, fields of lupine burst into a cornucopia of color along the north shore of Lake Superior, in varying shades of purple and pink, blue and white.
Photographers love tall, showy, vibrant wildflowers. Images of Lupine grow on Facebook at this time of year.
Yet these images are often accompanied by critical commentary, pointing out that the lupine now spreading in northeast Minnesota is not native to the state.
Indeed, the lupine presents a nice paradox, a beautiful plant that potentially damages the ecosystem of the region.
“It’s a double-edged sword,” conceded Beth Miller, a retired teacher and self-proclaimed “nature nerd” who is also a photographer and enjoys capturing lupine images.
“There are so many different color combinations,” she said, while gazing at a large patch of lupines beside some train tracks just uphill from Duluth.
“So you have one here that’s blue with a white center and you have another layer that’s blue with a pink center.”
But she is also conflicted about them. This species of lupine, called big leaf Where big leaf lupine, comes from the west coast. Gardeners first brought it to the Midwest. Now it is found throughout the northern United States, and for the past ten years or so, it proliferated, especially along the north shore of Lake Superior.
“It chokes out other wildflowers that might grow in that ditch that are native, like that might be a habitat for Little yellow slippers“, Miller said. “But they can’t compete with lupine which is a more aggressive plant.”
Recently, Miller has started post photos of attractive native wildflowers such as columbine. But people are passionate about lupine.
“Usually people have a pretty strong opinion that they like the plant,” said Superior National Forest plant ecologist Jack Greenlee.
Occasionally, the Forest Service sprays patches of lupine with an herbicide, so it doesn’t spread to nearby areas that have been logged or treated with prescribed fire. And when they do, Greenlee says he often hears about it.
“It’s like, ‘oh, it’s such a pretty plant, why are you killing it?'” Greenlee says it’s a comment he gets a lot. Others say it does no harm.
Greenlee uses these conversations as opportunities to educate people. Lupine can out-compete native species, Greenlee tells them, and once it gets a foothold, it stays.
“I don’t know if I’ve ever changed anyone’s mind,” he said. “But it’s an opportunity to talk to people and at least let them hear the other side of why we care.”
Greenlee classifies lupine as having a “moderate” ecological risk. It’s not as damaging as invasive species such as buckthorn, he said. But it can spread quickly and dominate areas once established. And because it has deep root systems, it is difficult to eradicate.
Brooke Haworth, regional plant ecologist for the Minnesota Department of Natural Resources, says lupine isn’t creating a huge problem at this point.
It is not considered a noxious weed by the Minnesota Department of Agriculturewhich manages invasive plants with a major economic or environmental impact.
Anthony Cortilet, who oversees the noxious weed program for the Department of Agriculture, said he has received requests for evaluation of the bigleaf lupine.
“As you can imagine, everyone has a favorite plant that they don’t like. However, not all invasive plants are noxious weeds,” he said.
DNR’s Haworth said lupine has what she calls an “invasive tendency.”
“It will drive out other native species and take over their habitat,” Haworth said. “It overpowers them, and therefore it reduces the biodiversity of native species.”
It can have cascading impacts, she said. For example, native insects have adapted over time to depend on native plants, and native birds in turn depend on those native insects. Non-native plants can disrupt this chain.
There’s also a wild lupine native to Minnesota that the non-native plant could potentially out-compete, Haworth said.
Wild lupine is important because the federally endangered Karner Blue butterfly depends on them for food, just as monarch butterflies depend on milkweed. Non-native lupine does not offer the same benefit.
Wild lupine is most abundant in southeastern Minnesota. But the two species overlap in east-central Minnesota. If non-native lupine began to outcompete wild lupine and replace it in the landscape, it could cause problems for the endangered Karner Blue butterfly, Haworth said.
The Minnesota DNR actively manages lupine in state parks and trails along the North Coast. Liza McCarthy, MNR’s resource program specialist for parks, said crews cut it by hand or cut off the flower heads to prevent it from going to seed.
“In my opinion, we don’t need the added lure of lupine. Because the natural beauty of our natural and cultural resources in state parks and trails is wonderful as it is,” he said. she declared.
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