Abstract: It is important to evaluate the capability of heavy metal tolerance of high biomass grasses for developing bioenergy plants suited to heavily polluted environments, particularly metal pollutants, reducing the problem of bioenergy crops competing with staple food crops. Both switchgrass (Panicum virgatum) and guinea grass (P. maximum) are important bioenergy plants because of their high yield potential. These grasses were used to examine the effects of cadmium (Cd) on seedling growth under 0, 0.5, 5, 10, 20, 50, 100 μmol/L Cd for switchgrass, 0, 2, 5, 7.5, 10 μmol/L Cd for guinea grass grown using hydroponic techniques. Root and shoot fresh weights of both grasses were recorded and root morphological data of switchgrass were obtained using an EPSON scanner and WinRHIZO software. ICP-AES was used to examine Cd accumulation in switchgrass. The results showed that the biomass and root elongation of switchgrass and guinea grass were significantly affected by Cd. The root biomass of switchgrass decreased greatly under 50 μmol/L Cd conditions, but root biomass, shoot biomass, total biomass and root elongation in guinea grass were decreased by 86.1%, 83.5%, 84.1% and 96.3% respectively by the 2 μmol/L Cd treatment; root elongation in switchgrass was reduced by 55% in 5 μmol/L Cd solution. The Cd concentration in shoots of switchgrass was 40 mg/kg and the biomass was reduced by 45% in the 20 μmol/L Cd treatment. In addition, the root length and root tip numbers in switchgrass were significantly decreased in Cd treatments in comparison with the control. However, mean root diameter increased in Cd solutions. There was a significant negative correlation between root length, root surface area and root volume, and Cd accumulation and a strong positive correlation between root length, root surface area and root volume and TFs in the 0-1 mm mean root diameter class suggesting that fine roots may play an important role in Cd accumulation.