Epigenetics, a field of molecular biology, allows genetic information to be altered through the organism's response to environmental signals without changing the sequence of the DNA molecule. Epigenetic regulation is achieved by various epigenetic mechanisms and results in the characteristic on and off switching of genetic transcription. The most common plant epigenetic mechanisms that regulate chromatin structure are DNA methylation, histone modifications, noncoding RNA molecules and transposon elements. Alternative gene expression plays an important role in plant development, defense against repetitive elements and fast response to stimuli from the environment. The key importance of epigenetic mechanisms is the ability of plants to adapt to stressful and life-threatening environmental factors, especially in times of climate change, which strongly interferes with the life cycle of plants. Climate change causes severe physiological stress to plants, which is why they have developed high phenotypic plasticity through epigenetic mechanisms. Epigenetic changes can be inherited in the form of epigenetic memory to daughter cells and thus maintain transcriptional states and an appropriate response to environmental changes. The issue of climate change is growing and is causing faster changes than plants are used to, so in the future natural adaptation mechanisms may not be enough for plants to survive. Forest ecosystems, which are crucial for maintaining the natural balance, are particularly at risk.