Composting is a common practice for management of herbaceous yard materials and other decomposable materials. Although composting is promoted by state agencies for many materials, a notable exception is invasive plants due to concerns about spreading propagules with the finished product. To address this issue, we measured the viability of garlic mustard and common buckthorn seeds exposed to turned or static composting methods. Piles were built in 2012 and 2013, and seeds from both species were inserted and monitored for viability. Seed viability was reduced rapidly regardless of year, composting method, or species. Viability of seeds was zero within 7 and 15 d of composting for garlic mustard and common buckthorn, respectively, in both years. Results indicate that composting facilities are able to render the seeds of these invasive plants nonviable using either composting method because inactivation is within the composting timeframes typically practiced by the industry. This includes the process to further reduce pathogens (PFRP) with thresholds of 55 C for 15 d for the compost management process used for this trial.

Nomenclature: European buckthorn, Rhamnus cathartica L.; garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande.

Management Implications: Land managers will continue their efforts to control the spread of invasive plants in natural areas. These efforts will generate a volume of plant material that needs to be managed as a waste. This research demonstrates that the use of landfilling for disposal is not the only option available for garlic mustard- and European buckthorn-infested material. Well-managed compost facilities are more than capable of achieving the temperatures necessary to render seeds from these species unviable. Placement of the materials within static managed piles with proper moisture and carbon-to-nitrogen ratios create conditions that are favorable for the destruction of seeds from these species in a short time period. An additional practice that could easily be adopted would be to require placement of infested material in the center of the compost piles and leave them unturned for a period of up to 7 d. This would expose any seeds present to maximum pile temperatures, thus reducing seed viability while still allowing facility operators adequate time to meet the process to further reduce pathogens (PFRP) turning requirements. Other options for waste management include composting materials on site to produce a soil amendment, thus eliminating the cost of transporting and disposal of plants materials as currently practiced.