Miscanthus is a tall perennial grass species native to parts of Asia. It has the potential to produce relatively high dry matter yields across a wide range of environmental and soil conditions. The Miscanthus cultivar most commonly recommended for biofuel production is a sterile hybrid (M. × giganteus) of M. sacchariflorus × M. sinensis , but there are some challenges for its production. One of them is the occurrence of cold damage during the first winter after planting when plant losses can be high. These losses could be exacerbated by incomplete or late senescence. A field trial was established in spring 2010 with split-plot randomized complete block design with four replicate blocks to evaluate plant senescence timing and rates in nine different varieties of Miscanthus, and to evaluate their morphological characters and yield potential in Iowa. All varieties performed well in both years (2010-2011), with no plant mortalities in any of the variety. Photosynthetic C assimilation (A), stomatal conductance (g_s) and total leaf nitrogen (N) concentration ([N]) were measured beginning in late summer and ending at the first hard freeze as indicators of senescence timing and rates. All nine varieties of Miscanthus significantly differed in A, (g_s and leaf [N] (P = 0.0001, P = 0.0006, P = 0.0001 respectively). Four out of five Amuri-type varieties responded earlier to environmental signals for autumn and started senescence sooner and at a more rapid pace than the other six varieties of Miscanthus. Varieties also significantly differed for their morphological characters such as plant height (P < 0.0001), tiller density (P < 0.0001), basal circumference (P < 0.0001) and leaf width (P < 0.0001) were observed. Varieties were also significantly different for their above-ground biomass yields (P = 0.01), but no significant differences were observed between varieties for their below-ground biomass yields. In all varieties year had a significant difference (P < 0.0001) for all morphological and yield characters except stem diameter.