Miscanthus (Miscanthus x giganteus) is a fast-growing energy crop as it is possible to use its biomass in the production of various forms of biofuels. The essential characteristics of Miscanthus are tolerance to diseases and pests, high biomass yield and high efficiency of water-and nutrient-use. Depending on its further utilisation for energy purposes, Miscanthus can be harvested either in autumn or in spring. As a sterile crop, it propagates by either rhizome pieces or by older plantings obtained from micropropagation. The establishment success, along with agroecological conditions of cultivation site, mostly depends on planting material used. The paper aims to determine the yield of dry matter (t/ha), the number of shoots per plant, the content of dry matter (%) and the height of plant (m) in relation to the origin of planting material and two harvesting periods (autumn and spring). The research was conducted on a three-year establishment site of Miscanthus. Rhizomes from England and Croatia and older plantings from Poland were used as planting material. Biomass yield was determined in autumn (November 2018), and spring (March 2019) harvest, whereas the height of plants and the number of shoots were determined at the end of the growing season. According to the research results, the type of planting material significantly influences the Miscanthus height, the number of its shoots and the yield of its biomass. Likewise, different harvesting periods impact the yield and content of dry matter in harvested biomass substantially.