What to do when there's not enough sun.
Grasses are sun-loving plants, for the most part. For healthy growth, lawn grasses need at least 4 hours of direct sun a day. If they receive much traffic or wear and tear, they need a minimum of 6 hours.
In addition to being weak from lack of sun, grass in shady areas can suffer more diseases because of cool, moist conditions and lack of air circulation. Poor grass stands in shady areas are vulnerable to erosion, which can carry sediments and other pollutants into surface water.
Here are some options for coping with shady areas:
Choose the right grass. In spots that get marginal light, plant fine fescues, which are more shade-tolerant than other lawn grasses.
Grow other ground covers. Grass isn't your only choice. Consider attractive and vigorous shade-loving groundcovers such as:
Lily of the valley
Plant a shade or woodland garden. There are hundreds of herbaceous perennial flowers and foliage plants that will thrive in shade, as well as annuals such as impatiens.
Mulch around trees. If you don't have the energy to maintain a shade garden, consider using about 3 inches of wood, bark, or stone mulch around the base of trees. (Don't pile mulch against the base of the tree trunk.)
Build paths. If grass grows fine in your shady areas except where people walk, put in a stone, gravel, or other type of path to concentrate wear and tear in one area.
Mow high. Grass in shady areas should be allowed to grow taller than grass in direct sun. Do not mow any closer than 3 inches.
Fertilize and water less. Grass in shady areas grows slowly and needs less fertilizer and water.
Let in more light. Remove lower branches and selectively prune other branches or remove entire trees to let in more light.