Epigenetics is defined by long-lasting or heritable changes in gene expression that are not associated with changes in DNA sequence. It is mainly reflected in methylation of DNA and chemical changes in DNA-associated chromosomal proteins such as histones. Recognition of its importance as a means for control of plant development has increased significantly in recent years, however, little is known about epigenetic controls in the life of trees and other woody plants. Many traits important to biomass growth and adaptability in trees may be under epigenetic control, thus may be useful for their breeding and biotechnology. This includes timing of flowering and flower structure; dormancy induction and release; shoot and leaf architecture; amenability to organ regeneration; stress tolerance; and phase-associated changes in wood structure. We will use poplar (genus Populus, including aspens and cottonwoods), because it has been designated as a model woody biomass species for genomic studies, and is a major source of wood, energy, and environmental services in the USA and throughout the world. We will characterize epigenetic changes in DNA methylation and two kinds of histone modification via a combination of antibody-based chromatin immunoprecipitation and DNA sequencing (“ChIP-sequencing”).