Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

摘要

The National Wildlife Refuge System has an active habitat restoration program and annually seeds thousands of hectares with native plant species. The noxious weed, Canada thistle (Cirsium arvense), plagues these restorations. This study evaluates planting methodology and seed mixes with the goal of recommending optimal methods to reduce infestation of noxious weeds, especially Canada thistle, in new restorations. Three planting methods (dormant season broadcast, growing season (summer) broadcast, and growing season (summer) drill) were fully crossed with three levels of seed diversity (10, 20, and 34 species (plus a fourth level, 58 species, on the three sites in Iowa)) in a completely randomized design replicated on nine sites in Minnesota and Iowa. The propagule bank of Canada thistle was evaluated at each site. Planting occurred in winter 2004 and spring-summer 2005. Here I report on results through summer 2007. None of the planting methods or seed mix diversities consistently resulted in reduced abundance of Canada thistle.