Let the grass in the shade grow a little longer. The grass blade is like an antenna, the longer it is the more light it can absorb. Increase air movement. Air circulation is critical for growing grass. Choose fences with alternating boards instead of solid. Reduce fertilization. Grass in the shade does not require as much fertilizer as grass in the sun. Increase reflected light. Change the color of your shed or fence from brown to white. The reflected light can be used by the grass. Thin the center of large trees. Thinning branches in the center of a tree should not reduce the privacy or beauty the tree provides, however, mid-day sun will filter down through the tree to provide additional light for the grass. Use a shade tolerant grass. "American Shade" is perfect for areas of your lawn that receive between 2 and 6 hours of sun light.