Lupine, a controversial plant

Flowering lupines

Photo by Dusty Warner, NPS

In years past, there was a species of Lupine that was native to Maine, Lupinus perennis, but it is now so scarce that it is nearly extirpated from the state of Maine. As you are driving the highways and byways in Maine in the spring you will almost always see a beautiful carpet of pink and purple picturesque flowers. This plant is not native to Maine. It is Bigleaf lupine, Lupinus polyphyllus, which originated in the western United States. This plant was introduced to Maine as a landscaping plant, and quickly got out of control. It is what we refer to as an invasive species. In a nutshell, it is an invasive plant that can crowd native species out of their preferred habitats. Also, their seeds are toxic to animals if too many are consumed, which could threaten both grazing farm animals and native herbivores.

This does not mean that Bigleaf lupine is always harmful, however. It is a good source of nectar for pollinating insects and has been known to attract hummingbirds. This plant also provides regulating ecosystem services, as it has deep roots that help prevent erosion, as well as supporting services, as it is a legume and thus fixes nitrogen and returns it to the soil.

These invasive plants along roads in the park have been controversial. The National Park Service prioritizes protecting native species and works to eliminate nonnative invasive species. Currently, the park removes Bigleaf lupine when it encroaches upon natural habitat.

This species spreads like any recognized invasive plant and it has displaced both rare and common Maine plants. Lupine could have an impact on the migratory monarch butterfly because it crowds out native milkweed. The larva of the monarch depends on milkweed as its host plant; it cannot eat lupine.

Outside of the park anyone is free to grow the nonnative species. Bigleaf lupine in its native range – the Pacific Northwest – is an integral part of some western ecosystems. But we should not assume that Bigleaf lupine in Maine is harmless.