Poplars (Populus spp.) are fast-growing trees that can be successfully grown from stem cuttings. Lombardy poplar (Populus nigra) and hybrid poplar (Populus deltoides x nigra) are hardy in U.S. Department of Agriculture plant hardiness zones 3 to 9, while the tulip poplar (Liriodendron tulipifera) is hardy in USDA zones 4 to 9.
In poplars, as well as many other species of woody plants and trees, rooting hormones are stored in the vicinity of buds or undeveloped leaf nodules. When exposed to heat and moisture, roots develop at these sites to produce new plants. The practice of producing new trees and shrubs from stem cuttings is called vegetative propagation. Whereas growing plants from seeds doesn't always produce the desired result due to the hybridization of different varieties, growing a poplar tree from a stem cutting assures that you will get the exact same type of tree, or clone, as the parent tree. Whether you are growing one poplar tree or many, using your own poplar cuttings saves money and produces quick results in a very short time.
According to North Carolina State University, "The four main types of stem cuttings are herbaceous, softwood, semi-hardwood and hardwood." The categories refer to the growth stage of the parent, or stock, plant, and is important to consider when deciding when to take cuttings. Their classification as woody plants means that poplars can be propagated by means of softwood or hardwood cuttings, each of which is done at different times of the year. Softwood cuttings use the new growth on a poplar tree just before it matures or hardens. Shoots growing at the base of the tree or elsewhere along its roots can also be used and generally appear between May and July. Hardwood cuttings are done in late fall to early spring and are taken from dormant mature stems.