One of the first steps in ecological restoration is often controlling invasive weeds, which can be a major barrier to native plant establishment. But what happens after restoration is complete? At most sites, weed pressure is an ongoing challenge that land managers must grapple with to maintain the diversity, structure, and functioning of native plant communities.

The Invasive Weed & Restoration Ecology Lab at UC Davis is currently exploring the use of “competitive planting” as a method for weed suppression in restored grassland communities. As part of a USDA-funded project, we are evaluating what seed mixes can best facilitate the establishment of native perennial bunchgrasses while also preventing reinvasion of problematic weeds, in particular invasive annual grasses. Some of our preliminary results suggest that including native annual wildflowers along with native grasses could be the best way to increase “invasion resistance” in restored California grasslands. This approach could improve the long-term sustainability of restored grasslands while also reducing management inputs required to control invasive weeds.

Graduate student Olivia Parra collects data on the abundance of native and nonnative plant species in experimental restoration plots established from different seed mixes.