Lack of sunlight
If the lawn has too much shade, the grass may not be developing roots and will become notably thin. How to improve lawn in shaded areas? Pruning trees to increase sunlight and the addition of a shade tolerant seed very early in the spring (end April or beginning of May) are the best solution.
My lawn has difficulty to grow in the shade?
It is normal; the type of grass which develops in the shade is mainly of the family of the fescues, a kind of grass that is rather fragile and sensitive. Each seed of fescue makes only one grass blade. The Kentucky blue grass, which is sold in sod, needs approximately 5-6 hours of sun exposure every day for good development. It would be preferable for the shaded area to be overseeded, every spring, with seeds especially for shaded area.
My lawn is very thin under my trees. How to improve the situation?
It is a normal situation, because this is a very competitive zone. The roots of the trees and the lawn are sharing the water, nutrients and sun exposure. To improve the situation, you could, if possible, prune some branches to provide more daylight to turfgrass. Furthermore, you could, every spring have a routine: buy some bags of garden soil and an excellent seed for shaded area. If the situation is impossible to correct, you could make a flower bed with plants suitable for shade.