Healthy grass requires light, air, water, and nutrients. Trees, tree roots, shrubs, and buildings that shade your yard can prevent your lawn from getting the necessary nutrients. Allow more light to reach your grass by trimming trees and shrubs. Increase mowing height to allow your grass to capture more sun, and to promote a stronger grass root system. Limit the amount of foot traffic in the problem area. Monitor the condition of your lawn closely, and adjust irrigation and fertilizer schedules as needed to help any trouble spots.