If your property is shaded by established trees, you might to choose to work with your existing landscape and plant perennials that naturally thrive in this environment. There are many kinds of perennials that grow in the shade. Though many are grown for their interesting foliage, some perennials also flower well in shade.
Some of the most common shade perennials are: Hostas, Ferns, Foamflowers (Tiarella), Astilbe, Brunnera, Lily of the Valley (Convallaria), Bleeding Heart (Dicentra), Lenten Rose (Helleborus), and Lungwort (Pulmonaria). Searching the Perennial Encyclopedia will reveal even more shade loving perennials.