DNA isolation is a fundamental technique for all molecular biology laboratories. Depending on the plant species, DNA isolation can be challenging. In particular, adapted protocols rarely exist for tree species which are not used as standard model organisms. Here, we describe a flexible DNA isolation protocol that works for 59 tree species in a modular system. It is based on an ATMAB-containing extraction buffer to which proteinase K and/or boric acid are added, depending on the plant species. Subsequent purification steps include one or two precipitations with dichloromethane and, depending on the tree species, an optional sodium acetate precipitation. Using leaf material of a hybrid poplar clone from