Wild Lupine

Photo by M. Demmon, on the website for the Herbarium of the University of Michigan, michiganflora.net

By Sarah Fuller

A search for May flowers at Kankakee Sands will yield a diverse collection.   One particularly easy find is wild lupine (Lupinus perennis).   Its eye-catching, bright blue flowers love the dry, sandy openings in the prairies and oak savannas of Northwest Indiana and Northeast Illinois.   Wild lupine, also called sundial lupine, flourishes in disturbed sites with little shade, such as recently mowed or burned areas.  Since its flower production increases after a fire, the standing swatches of blue are likely to be dense in locations that were burned this spring or last fall.

Wild lupines have plump, blue, pea-like flowers along the 8- to 24-inch reddish green stems.  The round, compound leaves have up to 11 leaflets.   These perennial legumes sprout in late March and April, flower from May to June, and by July will have a pod full of seeds ready for dispersal.   The above-ground plant material will start dying back in August, but the deep taproot can live for multiple years.

Although the flowering lupine stalks may remind me of blue corn on the cob, it is much more useful to remember that the wild lupine’s ecological processes are more closely related to peas.   Like many other plants within the pea family, lupines add nitrogen to the soil.  Just as farmers use soybeans (another legume) to improve soil nutrients, lupines perform the same function in a prairie.  Lupine roots have nodules containing bacteria that convert nitrogen gas from the air into ammonium—a compound of nitrogen and hydrogen.  The ammonium is then released into the soil and can be absorbed by roots of neighboring plants.   The lupines’ nitrogen fixing capabilities may be especially important after a fire, since surface nitrogen is lost during a burn.

While contributing nutrients to help adjacent plants grow is a distinctive aspect of this prairie flower, nitrogen fixing is not its only noteworthy feature.   Wild lupines are the perfect (and only) food for three species of butterfly.  The larvae of the Karner Blue (Plebejus samuelis), a federally endangered butterfly still present in the dunes just south of Lake Michigan, is one of the species dependent on lupine leaves.  Similarly, the Persius Duskywing (Erynnis persius persius) larvae consume the leaves and are endangered within Indiana.  The Frosted Elfin (Callophrys irus irus), and its bud-eating larvae, are threatened within the state of Indiana. These butterflies, while not documented in Newton County, are all present just to the north in Lake County.

Remember that as you spot batches of wild lupines, there’s no need to be as picky as the caterpillars, who have eyes only for lupines.  Take the time for your eyes to feast on the surrounding flowers benefitting from the wild lupine’s nitrogen fixation as well.   Enjoy the entire floral array of eye candy the prairie has to offer this May.

Sarah Fuller is an Ohio native and graduate of Cornell University.  She is working as a seasonal Restoration Management Assistant at Kankakee Sands, through a partnership with the Student Conservation Association. Sarah is working alongside her other crew members to maintain suitable habitat for all prairie and oak savanna species – especially wildflowers.

The Nature Conservancy’s Kankakee Sands of Indiana and Illinois is 10,000 acres of prairie and savanna habitat in Northwest Indiana and Northeast Illinois, open every day of the year for public enjoyment.  For more information visit www.nature.org/KankakeeSands or call the office at 219-285-2184.

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