Methane yields from silage made from switchgrass- and reed canarygrass-seeded plots with two N application rates and three harvest dates were assessed in Eastern Canada. The average specific methane yield from reed canarygrass-seeded plots (0.187 (N)L CH(4) g VS(-1)) was less than from switchgrass-seeded plots (0.212 (N)L CH(4) g VS(-1)). Switchgrass did not establish well and made up only a small proportion of the DM yield. As a consequence, the average methane yield per hectare from reed canarygrass-seeded plots (1.37 GL CH(4) ha(-1)) was significantly greater than switchgrass-seeded plots (0.91 GL CH(4) ha(-1)). Increased N fertilization reduced specific methane yields but increased methane yield per hectare, primarily because of increased DM yield. Delaying harvest resulted in decreased methane yields per hectare and specific methane yields, particularly for reed canarygrass. Further long-term research could help identify important factors influencing methane yields from crops during a complete stand life cycle. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.