yes, aspen is aggressive trees. But we also have spruce, pine, willow, birch and a whole bunch of other verities to look after as well. In fact, the aspen tree is the one that the pulp industry modified (GMO) tree to plant for pulp harvest. It is supposed to be sterile but my heart tells me that it will cross pollinate with the verieties here and cause all kinds of problems. They are also modified to grow VERY fast. They can be harvested as full grown trees in 20 - 25 years.