Given adequate rainfall and the right range of soil acidity trees will seed and grow themselves. This town was farm fields in the 1930s. Some trees were planted when the streets were laid out and houses built. Others, particularly ornamentals, continue to be planted. But there are a great number of trees that are volunteers that have been allowed to mature over the last century. Norway maples, sweet gum, tulip poplar, and red oak are particularly good at volunteering.
We have mullberry, maple, boxelder, and sometimes oak trees that spring up everywhere and basically need to be weeded before they get too big. Mullberry is particularly "weedy", a common sight at the edge of fences or in hedges.
