Cross over to Bar Island at low tide in June and July, and soon you’ll discover fields of majestic purple, blue and pink lupine wildflowers of Acadia, beckoning to be admired and photographed.

Squeezed along the edge of the fields stands a less showy plant – common milkweed – which could be missed if not for a sign calling this place a “Milkweed Habitat.”

These fields may be the site of a coming showdown between lupine and milkweed that could affect the fate of monarch butterflies in Acadia National Park.

As photogenic as the spiky tall flowers of the western lupine are, they are invasive non-native plants, threatening to crowd out the homelier milkweed critical to the lifecycle of the monarch, which recently became candidate for listing under the US Endangered Species Act. The faceoff between lupine and milkweed and the monarch could eventually come to a head on the island, just off the coast of Bar Harbor.

“If the western lupine is encroaching on critical habitats in the park…it would be a very high priority to remove it,” said Amanda S. Pollock, Acadia public affairs officer, in an email. In years past, the park’s Invasive Plant Monitoring Team “removed lupines encroaching on a significant area of milkweed to protect habitat for the soon to be listed as endangered monarch butterfly.”

Pollock said the team has managed lupine encroaching on milkweed on Bar Island, Fernald Point, and a small area near Great Meadow Drive. She said the team has removed lupine on Bar Island “but only a section of the field, near the milkweed and the path.”

The park has not planted any mature milkweed, but resource managers have spread seed in areas where milkweed would likely grow well, including Bar Island, Pollock added.

Removal of lupine wildflowers of Acadia stirred controversy in 2005

Nearly two decades ago, the park’s removal of some of the invasive non-native lupine stirred such public outcry, including from organizers of a Down East lupine festival, officials stopped the effort to study the issue further.

In an interview last week, consulting botanist Jill E. Weber recalled the literature she reviewed and the field research she conducted around that time to share with the park. Even then, before monarchs were as much of a concern as now, her findings raised questions about how invasive the non-native lupine could become, she said.

The plant – known scientifically as Lupinus polyphyllus and also commonly as garden or bigleaf lupine – is native to western parts of North America, but when introduced to other areas, it can spread like wildfire.

In New Zealand, it took hold in gravelly riverbeds, affecting the nesting of certain native birds. In Norway, it started overwintering in the 1930s. And in Maine, it wasn’t noted in the classic 1894 “Flora of Mount Desert Island, Maine: A preliminary catalogue of the plants growing on Mount Desert Island and the adjacent islands.” So for it to be so prevalent now, “its spread has been pretty quick,” said Weber.

And when she found the invasive lupine – once thought to be limited to disturbed areas like roadsides and fields – virtually in standing water in the Acadia wetland known as the Great Meadow, Weber said she was surprised.

Several years after her lupine literature review for the park, in the 2010 book The Plants of Acadia National Park, Weber and her co-authors had this to say about garden lupine: “Though locally beloved, this species is invasive in the Midwest and has invaded at least one wetland in our area.” (PLEASE NOTE: See sidebar about Amazon.com links)

Weber said last week that “I don’t think it’s public enemy No. 1,” but “with climate change it may be changing its behavior.”

How non-native lupine became widespread, beloved in Maine

A classic children’s book, Miss Rumphius, by Maine author and artist Barbara Cooney, tells the story of Alice Rumphius, who fulfilled a childhood promise to her grandfather to “make the world more beautiful” by sowing lupine seeds along roads and stone walls, across fields and headlands. (PLEASE NOTE: See sidebar about Amazon.com links)

According to the New England Historical Society, a publisher of online articles and books, the character was based on a real-life Lupine Lady in Maine, Hilda (Edwards) Hamlin, citing a story about her in Yankee magazine in 1971. She lived in Christmas Cove, Maine, not far from Cooney’s home.

So beloved was the story of Miss Rumphius, it won the American Book Award in 1982, and the Maine Library Association has been giving the Lupine Award annually since 1989, in the picture book and juvenile / young adult categories, to a living author or illustrator who resides in Maine, or whose work is set in Maine.

Cooney’s original art, featuring lupines painted in acrylics with accents of Prismacolor pencils on gesso-coated percale fabric mounted on illustration board, according to the 30^th anniversary edition of the book, is in the collection of the Bowdoin College Museum of Art in Brunswick.

While the writings about the real-life and fictional Lupine Lady don’t seem to distinguish between non-native lupine and the one that is native to Maine – the sundial lupine – the fact that the smaller, more modest lupine (Lupinus perennis) is rarely found in the wild in the state, and may even be extirpated, indicates it’s the flashier invasive Lupinus polyphyllus that’s been spread around.

Efforts to manage lupine wildflowers of Acadia and other invasives

With such a history behind non-native lupine, it’s no wonder attempts to manage its spread can be controversial.

But that’s not keeping non-native lupine off the 25 target invasive plant species monitored every year by the park, even if the species of most concern are currently glossy buckthorn, Japanese barberry, Morrow’s honeysuckle, Japanese knotweed, and Canada and bull thistles.

And it’s not keeping the state Department of Agriculture, Conservation and Forestry from putting the lupine on its “Advisory List of Invasive Plants,” to alert the public that it poses a threat to habitats and natural resources in Maine. The lupine didn’t make the state’s “Do Not Sell” list for the horticulture trade, however.

Interestingly, in the hierarchy of worrisome invasive plants, another non-native found in Acadia – rugosa rose – doesn’t make the park’s target 25 species, but the state is now calling it an “Invasive Terrestrial Plant Species of Special Concern.” Beginning in 2024, Maine retailers will be required to label rugosa rose as “Invasive Species – Harmful to the Environment,” along with providing instructions for preventing spread and non-invasive alternatives. It’s the first plant to fall under this state regulatory category.

Research, plant management to help monarch butterfly in Acadia

Even back in the 1930s, in a park publication entitled “Nature Notes From Acadia,” a state scientist noted the dwindling population of monarch butterflies as well as the shortage of milkweed that the larvae, or caterpillars, feed on.

“Local observers stated that the Monarch had been very rarely found here due to the absence of its food plant. In 1932 one or two individuals were seen,” wrote A. E. Brower, assistant state entomologist for the Maine Forest Service, in the September-October 1934 issue of the notes. “Lack of milkweed plants prevents its breeding in this locality,” wrote Brower, who lamented not seeing even one monarch on a visit to Acadia in 1931.

Ever hopeful for the monarch, Brower wrote, “May its numbers long swell like the breakers which roll up on Acadia’s granite shores.”

These days, its numbers are still not swelling. But near the top of Cadillac Mountain during the annual HawkWatch and along Acadia’s granite shores and elsewhere during periodic “bioblitzes,” researchers and citizen science volunteers have been counting monarch butterflies as part of the attempt to better understand and protect the migratory insect.

Last year, on Sept. 3, a sunny to mostly sunny day, a total of 21 monarchs were counted atop Cadillac, leading the observers to exclaim in their hawkcount.org non-raptor notes, “Fabulous Monarch day!” And on Sept. 18, under cloudy skies, “impressive Monarchs! 12 in this weather!”

And through projects documented on iNaturalist.org, the park’s citizen science volunteers recorded 6 sightings of monarch butterflies over 2 days in July during a 2016 National Parks BioBlitz, and a running total of 152 monarchs in a separate ongoing Acadia National Park biodiversity project. That Acadia project also has cumulatively documented 76 observations of common milkweed and 106 observations of the invasive lupine, as of this writing.

But perhaps the greatest effort to bring back the monarch in Acadia will rely on planting and protecting milkweed, as that is where monarchs exclusively lay their eggs, and what the caterpillars eat, as the milkweed sap provides them with special chemical defenses against predators.

In 2015, Acadia was one of 50 national parks that received special funding to map milkweed habitat and document caterpillar and other life stages of the monarch. As part of the effort to help the monarchs, the park planted milkweed at Hulls Cove Visitor Center and elsewhere in Acadia.

What can a lover of lupine AND monarch butterflies do?

• Plant milkweed native to Maine, or wherever you live: The four species native to Maine, according to the Wildseed Project, are common, swamp, butterfly and poke milkweeds. For native milkweed for other parts of the country, refer to this National Wildlife Federation article.
  

  Look closely and you can see Maine’s native sundial lupine planted this spring by the Bar Harbor Garden Club along the Hulls Cove Visitor Center parking lot.

• Plant sundial lupine, native to Maine but now rare to find in the wild: This spring, the Bar Harbor Garden Club planted some of the Maine native lupine in a traffic island along the Hulls Cove Visitor Center parking lot, marked by a sign, “Lupines: Native or Invasive?” The park sign also highlights the concern about invasive lupine crowding out milkweed critical for monarchs. While the sundial lupine may not have historically been found on Mount Desert Island, according to consulting botanist Weber, officials point to it being the only food source for the federally endangered Karner blue butterfly. The garden club received a Maine Arts Commission Bicentennial Grant for its sundial lupine project and hopes to see enough Lupinus perennis re-established in the state so that the endangered butterfly may be reintroduced.
• Keep bigleaf lupine in your garden from becoming invasive: After the invasive lupine is done flowering, remove the seeds and any lupine you see starting to spread beyond the intended area. “You can still have it in your yard,” said botanist Weber, but if you also know that it can displace milkweed important to monarchs, “no one needs to tell you to obey new rules.”