Developement is the biggest threat to what’s left of this northwest prairie, home to imperiled plant species like Bradshaw’s lomatium, the Willamette daisy, and Kincaid’s lupine. The Fender’s blue butterfly, once considered extinct, is dependent on lupines for survival. Off-road activities disturb or destroy natural habitats, and introduced species threaten to choke out rare native plants. Until 1989, entomologists had crossed the Fender’s blue butterfly off their lists. As far as they could tell, it was gone. Kaput. Finito. Extinct.
And then they found them again, in this surviving sliver of native wet prairie on former farmland remarkably close to downtown Eugene, Oregon. Not surprisingly, the butterflies were found close to where the rare Kincaid’s blue lupine grows. That makes perfect sense; the Kincaid’s blue lupine is the only place where the Fender’s blue will lay its eggs. Its larvae remain there, feeding on the bright purple flower spikes, for nearly a year. In late spring, the larvae hatch into adults, beautiful dark-blue butterflies about an inch long. As adults, they will feed on a wider variety of wildflowers. But that only lasts for 9 days before they lay their eggs—on the lupine, of course—and then die. The new larvae snuggle into the lupines, and the whole cycle begins again.
That’s what happens when you preserve the old-time habitats. Spreading over 508 acres (206 hectares), Willow Creek Preserve is an intact remnant of the upland grasslands, ash woods, and perennial streams that used to cover this Northwest river valley. It’s estimated that 99.8% of the native wet prairie has been lost to development since the 1940s. But here along Willow Creek, more than 200 native plant, 100 bird, and 25 butterfly species survive in healthy diversity. In late spring you’ll find the starlike yellow clusters of the endangered Bradshaw’s lomatium, while tall feathery blue camas perfectly complement snug yellow buttercups as they grow side by side in an open meadow. In midsummer, the endangered Willamette Valley daisy arrives, with its fat yellow center and pinkish ray petals. Lacy Oregon white-topped asters come along at the end of the summer.
In adjacent areas, trees and shrubs have taken over the native prairie; at Willow Creek, periodic burning holds them back, as nature intended, and lets the sunloving flowers maintain their territory. (Bradshaw’s lomatium, in fact, has increased by 50% in the areas where fire has been used to manage growth.) Non-native species like Scotch broom and Himalayan blackberry that have driven out the original species are regularly cleared out. Where the waist-high, fine-leaved tufted hairgrass should dominate, volunteers tear out the tough common teasel, an invasive thistle that’s trying to take over. Sure, it takes a lot of work—but one glimpse of a Fender’s blue butterfly makes it all worthwhile.