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While hiking the Minnesota Valley National Wildlife Refuge prairies at Rapids Lake and Old Cedar Avenue, have you ever seen bright blue and purple flowers that resemble a pea? This beautiful plant bears unique and important qualities and is threatened by human development in its natural habitat.
What is Wild Lupine?
Wild lupine, Lupinus Perennis, is also called sundial lupine because of its tendency to face towards the sun. From the family Fabaceae (legume, pea or bean family), wild lupine grows elongate clusters of blue-purple, pea-like flowers that are rich in nectar. This native perennial can be found in parts of the Midwest, northern east coast and southern states, thriving in sandy, sunny and windy conditions with little competition from weeds. These plants prefer cool weather for growing and are often blooming from May to June. They are somewhat short-lived, though, as these flowers die down in the summer heat during July.
One of the cool and most unique features of wild lupine is its exploding seedhead. Yep, you read that right! They have hairy, pea-shaped seed pods that ripen around midsummer. Turning black when mature, the seedheads open forcibly and eject the seeds several feet from the parent plant to disperse them as far as possible and increase the likelihood of germination 鈥 the sprouting of the seed into a plant. If you happen upon some wild lupine in early July, don鈥檛 be surprised if you get (softly) bombarded with Lupine seeds 鈥 speaking from personal experience! Spotted Touch-me-not, or Jewelweed, is another common plant found on the refuge that uses this seed dispersal method as well.
The History of Wild Lupine
The genus Lupinus stems from the Latin word 鈥榣upus,鈥 meaning 鈥榳olf.鈥 It was mistakenly thought that these plants wolfed down or robbed the soil of its nutrients. Wild lupine is actually a nitrogen-fixating plant, meaning it enhances soil fertility by fixing nitrogen from the air into a useful form that can be absorbed by organisms. Nitrogen fixation allows lupine plants to tolerate nutrient-poor soil, like its preferred sandy habitat. While sandy habitats lack significant nutrients, they also drain water freely. Like many other prairie plants, lupine grow a long taproot that penetrates the soil to a great depth in order to obtain adequate water.
Though beautiful to look at and a useful nitrogen-fixator, why should we care about wild lupine? Like most flowers, they are often utilized and relied upon by local wildlife. The vibrant blue-purple and nectar-rich flowers attract pollinators like bees, butterflies and hummingbirds. Being native to many parts of Minnesota, wild lupine holds special value to native bees and bumble bees, specifically mason bees, mining bees and small carpenter bees in search of pollen. Other wildlife, such as deer, browse lupine foliage, while birds and small mammals will eat the seeds. It is important to note that the consumption of wild lupine seeds is not recommended for humans and domesticated animals, like cats, dogs and horses, as the seeds can be toxic and potentially fatal if ingested in large quantities.
Endangered Karner Blue Butterfly
Native to different parts of North America, wild lupine is important in our ecosystems as a food source for wildlife and attracting pollinators, but there is one species in particular that has a very high demand for wild lupine. The federally endangered Karner blue butterfly relies on wild lupine as its larval host plant, meaning the caterpillar will only eat from these plants. You can find plants that have been grazed by searching for transparent areas on the leaves where larvae have selectively eaten only the green, fleshy parts. With the specificity of their habitat, these butterflies are unable to adapt to changes in their environment, leaving this species federally endangered since 1992 and protected under the Endangered Species Act of 1973.
Conservation Efforts
There are many areas across the country where loss of habitat threatens wild lupine, leading to a 90% decline in the number of plants since the Industrial Revolution. Human development has eliminated a large portion of viable habitat and limited its ability to reproduce. Factors of human development include habitat loss and fragmentation from farming and land development for commercial and residential use, as well as poor land management. Wild lupine habitat is hard to maintain, due to its tendency to flourish after fires or other forms of disturbance. Its seeds have a tough shell, making it hard to penetrate. Only the pressure changes from rapid heating or abrasion are strong enough to allow water to enter and begin germination. Although it sounds counterintuitive, without disturbance activities like fires, mowing or feeding by large ungulates, shrubs and trees invade lupine habitat and shade out the plants, greatly limiting any available habitat.
As the Karner blue butterfly has only a single host plant, suitable habitats are very limited. The decline in wild lupine is said to be causing the decline of the Karner blue butterfly. Human development and habitat fragmentation of wild lupine correlates to the small, isolated populations of the butterflies. In 2003, the U.S. Fish & Wildlife Service arranged the Karner Blue Butterfly Recovery Plan outlining strategies to recover the species by restoring habitat and stabilizing and recovering current populations.
What Can You Do?
Being that wild lupine is an attractive plant with its blue-purple flowers, many people want to plant them in their garden with the dual purpose of showing off their beauty and providing habitat for butterflies and pollinators. The enthusiasm for this effort is appreciable but be aware of the garden hybrids of lupine that have escaped to the wild. Large-leafed lupine, Lupinus polyphyllus, is an example of a non-native form of lupine that hybridized from gardening, now commonly found along roadsides, especially in northeastern Minnesota. Knowing exactly what seeds you are planting are crucial to preventing planting invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.
Learn more about invasive species .
If gardening is not in your wheelhouse, there are places around Minnesota Valley National Wildlife Refuge and across the Midwest to just simply view wild lupine. Keep an eye out at the Rapids Lake Education and Visitor Center parking lot prairie for wild lupine. Neighboring refuge Sherburne National Wildlife Refuge, just north of the Twin Cities, has a well-established population of lupine across various trails, such as Mahnomen, Blue Hill and the Oak Savanna Learning Center. The Prairie鈥檚 Edge Wildlife Drive, a one-way auto tour route, is the most popular viewing area at Sherburne Refuge, with the densest population of lupine is near the Prairie Trail within the first 2-miles of the wildlife drive. After viewing the lupine along the Prairie Trail, one must complete the rest of the 8-mile one-way drive, and there is plenty of other wildlife and vistas to see along this exciting wildlife tour!
While the Karner blue butterfly is considered extirpated in Minnesota, our neighbors to the east have stable populations of the species. Consider visiting Necedah National Wildlife Refuge in Wisconsin, a mere 3-hour drive from the Twin Cites. Here, there is an array of wild lupine and large populations of butterflies. Be sure to call ahead to schedule your visit with the first or second flight of the season during May or June. Don鈥檛 miss your shot at viewing these beautiful and unique plants before they鈥檙e gone for summer. If you鈥檙e lucky enough, you might find the Karner blue butterfly lurking around these plants. How cool would it be to say that you saw an endangered species and got thumped by an exploding seedhead? That could be once in a lifetime!
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