Lignin acylation, the decoration of hydroxyls on lignin structural units with acyl groups, is common in many plant species. Monocot lignins are decorated with p-coumarates via the polymerization of monolignol p-coumarate conjugates. The acyltransferase involved in the formation of these conjugates has been identified in a number of model monocot species, but the effect of monolignol p-coumarate conjugates on lignification, and on plant growth and development, has not yet been examined in plants that do not inherently possess p-coumarates on their lignins. The Oryza sativa p-COUMAROYL-CoA MONOLIGNOL TRANSFERASE gene (OsPMT) was introduced into two eudicots, Arabidopsis thaliana and Populus alba × grandidentata, and a series of analytical methods was used to demonstrate the incorporation of the ensuing monolignol p-coumarate conjugates into the lignin of these plants. In poplar, specifically, the addition of these conjugates did not occur at the expense of the naturally incorporated monolignol p-hydroxybenzoates. Plants expressing the PMT transgene can therefore produce monolignol p-coumarate conjugates essentially without competing with the formation of other acylated monolignols and without drastically impacting normal monolignol production.