Why is it hard to get grass to grow under trees?
Getting grass to grow under trees is not impossible but it is very difficult. For grass to grow in lawns, most grass varities need sunlight, water, and soil contact. Under trees it is hard to get sunlight and water and in some cases its even hard to get soil contact. The foliage from the trees prevents water and sunlight from accessing the soil surface and the roots of the tree often grow close to the soil surface. The roots not only suck up all the water and nutrients but sometimes they actually take over the soil. When this happens there is no soil for grass seed to germinate in and having grass is impossible.
Getting grass to grow under trees:
In some cases it is possible to get grass to grow under trees. If there is enough sunlight and you are able to water the lawn, getting grass to grow is possible but you should select a form of grass seed that performs better in shady areas. Here are some grass types that perform well in shade:
Creeping Red Fescue