AbstractElephant grass (Pennisetum purpureum Schum.) is a fast-growing native African plant species that produces commercially useful lignocellulosic biomass. It has been used in many countries to replace wood for paper, particleboard, and fiberboard. There is a close relationship between the mechanical properties of elephant grass cell walls and the performance of its products. The objective of this research was to investigate the cell wall mechanical properties at different growth periods of five types of elephant grasses, i.e., P. americanum cv. Tift 23A×P. purpureum cv. Tift N51 (HP), P. purpureum cv. Tift N51 (N51), P. purpureum cv. Huanan (Huanan), P. purpureum cv. Sumu No.2 (Sumu-2), and (P. americanum× P. purpureum) × P. purpureum cv. Guimu No.1 (Guimu-1). The hardness and elastic modulus of the cell walls were investigated by means of nanoindentation. The results showed that the hardness and elastic modulus of these elephant grasses increased as growth period increased. However, the rate of increase varied for the different types of elephant grass, which could help guide the evaluation of the properties of this kind of bio-fiber resource for the production of high-quality biocomposite products.