Two plots of restored prairie (IMAGE) Michigan State University Caption The experimental site Arbor Luxe Reserve let the MSU team investigate how planting year affected the trajectory of restored prairie. Native big bluestem grass is visible in the back, standing taller than the purple flowers of spotted knapweed in the front, which is native to Europe and generally considered invasive in North America. Credit Lars Brudvig Usage Restrictions Can use with credit. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.