Sunday, January 28, 2024

Look Closely at Wildflower and Pollinator Seed Mixes

A mock-up of a seed package showing a field of wild flowers and the words "Wildflower Mix."

If you’re thinking about sowing a wildflower or pollinator seed mix this season, you have lots of company.

Many people have been inspired to support pollinators by planting wildflowers to provide nectar and pollen. This increasing demand has spurred many companies to offer one or more seed mixes online or in retail stores. Caution is best, though, before choosing one. Look closely at the mix contents. “Wildflower” means different things to different people, and there could be surprises.

Consider the contents of this mix advertised for Minnesota:

Sweet William, Prairie Coneflower, Mexican Hat, Red Corn Poppy, Lance Leaf Coreopsis, Shirley Poppy, Wild Cosmos, Blanket Flower, Black Eyed Susan, Wild Perennial Lupine, Purple Coneflower, Russell Lupine, Plains Coreopsis, Siberian Wallflower, Scarlet Flax, Annual Red Phlox, Cornflower, Gloriosa Daisy, California Poppy, Perennial Blue Flax, Candytuft. 

Although these plants will likely survive in Minnesota, some are undesirable because they can grow aggressively, alter soil chemistry, or replace food sources that native insects or other animals are long adapted to using.

One example is Russell Lupine, also called Bigleaf Lupine. Known by the scientific name Lupinus polyphyllus, the plant is a garden favorite native to several western states. It has been introduced to the Upper Midwest, the Northeast, eastern Canada, and even Europe primarily for its ornamental value, but also for its deep, nitrogen-fixing roots that can stabilize and enrich soils.

In Minnesota, Russell Lupine has become especially abundant in the Arrowhead region, especially along roadsides through the north shore of Lake Superior. In spring and early summer, masses of the plants bloom in spectacular displays of white, pink, blue and purple. Their striking colonies are a big draw to that area each season. That’s good for the regional economy, but not so good for its environment. Beautiful though they are, the plants have some drawbacks.

Although Russell Lupine, L. polyphyllus, isn’t considered a noxious weed in Minnesota, the plant has several traits associated with invasive plants. It reproduces prolifically and grows in dense patches that exclude other plants, including native plants that have long supported pollinators. Although the plant declines in summer heat, it can grow in a range of other conditions, from moist to dry soils and full to part sun. That adaptability means it can grow in many habitats, from lakeshores and wetland edges to upland forest edges and roadsides. Its deep roots do help stabilize and enrich erodible, nutrient-poor soils – a useful trait for reclamation in the West – but deep roots also make the plant hard to remove from places where it isn’t wanted.

A mass of Lupinus polyphyllus along a roadside in northeast Minnesota. Photo copyright Peter Dzuik, 2004, and used with permission granted on the Minnesota Wildflowers website. 

Unfortunately, L. polyphyllus is sometimes mistaken for (and mislabeled as) our native “wild” lupine, Lupinus perennis. Now called Sundial Lupine to avoid confusion with “wild” Russell varieties, this perennial grows in prairies and savannas primarily in southeast and east central Minnesota and the eastern U.S.  

Like Russell Lupine, Sundial Lupine is beautiful, but more importantly it's critical for the survival of the federally endangered Karner Blue butterfly, Plebejus samuelis. Karner Blue larvae feed only on Sundial Lupine. Females lay their eggs on or near the plant – or what they judge to be the plant – and the caterpillars eat the leaves. Karner Blues are endangered in large part because Sundial Lupine has lost habitat, and as this larval host has become less plentiful, so has the Karner Blue.

Efforts are underway to bolster populations of Sundial Lupine, but where it overlaps with plantings of Lupinus polyphyllus, competition and hybridization present challenges. L. polyphyllus grows more aggressively and can displace L. perennis. The two species also hybridize, and unfortunately, neither L. polyphyllus nor its hybrids support Karner Blue larvae. If female butterflies lay eggs on either one, the larvae are unlikely to survive. 

Wildflower seed mixes, then, can include species that have both benefits and major drawbacks. To avoid problems like those caused by L. polyphyllus, it’s best to pause before choosing a mix. Study the contents and try to avoid species that can do more harm than good. Here are some steps to take:

  • The surest and easiest solution is to buy seeds and seed mixes from a local native plant nursery. The Minnesota DNR maintains a list of native plant suppliers. These growers are familiar with what should and shouldn’t be included in a mix, but if you prefer to do the work yourself, keep reading.
  • Look for scientific names of the plants in the mix. Different species may have the same common name, and plants with different common names may be the same species. Scientific names avoid this confusion by revealing a plant’s identity. If none are given, either don’t buy the mix or try to use the common names of the species to look them up.
  • Using scientific names, search for information about each species. Where is it from? Does it have a reputation for invasiveness? Good sources include the USDA Plants Database, EDDMapS, the Invasive Plant Atlas, and your state’s department of natural resources. Alternatively, search online using the scientific name of the plant followed by “invasive.”  
  • Be aware that plants native to the U.S. or North America are not necessarily native to your area. This may seem unimportant, but plants that come from another part of the country or continent can behave differently where they’re introduced.
  • Also be aware that maps showing native ranges can be wrong. The USDA Plants Database map for L. polyphyllus, for example, shows that the plant is native to much of the U.S. and Canada. But a plant guide from the USDA states that it’s native only to several western states and two western Canadian provinces..
A map of North America showing states and provinces where Russell Lupine is now found. Yellow stars placed on Alberta and Britsh Columbia in Canada and Washington, Oregon, California, Nevada, Montana, and Utah in the U.S. show where it originated.
Range of Lupinus polyphyllus, according to the USDA. States and provinces
shaded green are where the plant is said to be native. Yellow stars are added to
show where the plant originated.

  • As you read about the plant, look for invasive traits, such as rapid growth and prolific reproduction by seeds or vegetative parts. Phrases like “forms large colonies” and “naturalizes easily” are red flags, especially if the plant isn't native here. Comments from other growers can also be informative. One customer who grew Russell Lupine posted, “Lupines are growing everywhere, even the few seeds . . . tossed at the edge of the woods.” Sometimes pictures of a species provide a clue. If photos show an extensive carpet of plants (a monoculture), that plant is probably aggressive and could displace other species.

References and More Information

Wildflower and pollinator plantings

 Russell Lupine, Lupinus polyphyllus

Karner Blue butterflies

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