Unless there are tall trees in the SE to SW window of your sites location, tree shading should not be significant enough to prevent you from exploring solar options. A rule of thumb is to have no shading from 10AM to 3PM. Since the sun is higher in the horizon during the summer, tree shading usually provides more obstacles during the winter than in the summer. For regions that have overcast conditions and short days during the winter, such as the Puget Sound area, any but the worst shading issues can be worked with. Sunergy Systems can provide a complete site analysis to determine the exact shading and impact that any trees will have on your system.