Determination of the most critical stages of growth and development of Miscanthus × gigantheus

Purpose. To establish the growth and development patterns of Miscanthus × gigantheus and determine critical stages by response to environmental factors. Methods. Field studies were conducted in the zone of unstable moisture of the Right-Bank Forest Steppe of Ukraine at the experimental field of the Institute of Bioenergy Crops and Sugar Beets of the National Academy of Agrarian Sciences of Ukraine (50.023194, 30.173895) in 2020−2024. Results. Factors that can cause stress or lead to the death of miscanthus plants can be conventionally divided by the magnitude of impact into main and additional (i.e., those that enhance stress caused by the main factor) and by the degree of plant tolerance to those that can be mitigated and those whose impact is unavoidable. In this study, we do not consider global factors affecting plants, such as the absence of snow cover, because a drop in soil temperature in the root zone below −15–20°C along with the absence of snow cover will result in the death of not only miscanthus plants but also most winter cereal crops. We also do not consider factors that do not lead to plant death, such as low air temperature early in spring, as it only delays the emergence of leaves, as well as those, whose impact on the growth processes of miscanthus plants cannot be reliably assessed (additional stress factors). Thus, based on data processing and analysis of factors influencing the growth and development of miscanthus, the following critical periods can be identified: (1) macrostage 1 (leaf development) − spring frosts with a short-term temperature drop to −2°C, and (2) period of active growth and high water consumption − from macrostage 3 to macrostage 6. Conclusions. It the cultivation of M. × gigantheus, the most critical stages in terms of low air temperatures are BBCH stages from 00 to 19, and in terms of moisture deficit BBCH stages from 30 to 69.