In natural landscapes, trees and grass grow in completely different habitats. Turf grasses are full sun plants that grow best with a minimum of 6 hours of direct sunlight. It is rare to find turf growing in forested areas.
Typically, because of root competition for nutrients and moisture, in addition to the shade, the turf begins to thin out.
Studies show that trees grow best when they are properly mulched instead of having turf growing underneath them. Apply a 2-3 inch layer of wood chips or bark mulch leaving about a 6-inch buffer around the circumference of the trunk free of mulch. Avoid ‘mulch volcanos' (mulch piled up against the trunk) which causes bark injury. The mulch should extend underneath the dripline or canopy of the tree.
Tree trunks and roots are commonly damaged by lawnmowers and string trimmers. And a mulch layer can protect them from injury unlike turf.
How to grow grass in the shade
Contact a certified arborist to selectively remove branches and to thin out the tree canopy to increase the amount of sunlight. No more than ¼ of the foliage-bearing branches should be removed at one time.
Perform a soil test if you have never done one in the shady area or more than 3 years have passed since the last one. Apply lime and fertilizer according to the recommendations provided in the soil test results.
Turf-type tall fescues (needs a minimum of 4 hours of direct sunlight) and fine fescues, such as hard fescue, creeping red fescue, and sheep fescue are best suited for shady areas. Hard fescue is the best performer in the group. However, fine fescues do not handle foot traffic well, should be infrequently mowed, need at a bare minimum 2 hours of direct sunlight, and generally are planted on low maintenance sites.
Fertilize shady turf once a year in the fall.
Set mower height to a minimum of 3 inches and do not mow during the hottest, driest part of the summer.
Problems encountered when growing grass in the shade
Weeds like ground ivy and wild violets will invade shady areas because the grass tends to thin out and conditions are more favorable for the weeds.
Moss does not kill grass but begins to grow as the grass thins out.
Extra effort is needed to grow grass in the shade. It may be necessary to overseed yearly in the fall.
Consider growing a shade-tolerant groundcover in areas where the grass will not grow. However, do not plant invasive plants like English ivy, creeping euonymus, or vinca.