Answer: Shady conditions in combination with other plant stresses contribute to the difficulty of growing grasses under trees. For example, tree roots compete with turf for water and nutrients, and this competition can further weaken turf growing in shade. Excessive organic matter from leaf litter will also inhibit grass. One or more of these factors make it particularly difficult to grow grass under oak trees.
If you select grasses that have improved shade tolerance, such as fine fescues (hard, sheep, spreading, slender creeping and Chewing's), or tall fescues, you have a good chance of getting it to grow under oaks.
For the sake of your oak, you'll want to avoid using herbicides on the lawn, which could affect the roots of the tree.
Best wishes with your landscape!
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