Incompatibility

• Collect fallen oak leaves from around the base of the tree in the fall.Jupiterimages/Photos.com/Getty Images
  
  In addition to the competition for available light, water and nutrients that rages between oak trees and turf species, oak trees release a natural herbicide that hinders grass from thriving. Oaks release a chemical known as Coumarins that affects nearby grasses and herbs from growing. This chemical is absorbed into the soil directly from the roots of oak trees and from their leaves as they fall and collect on the ground around the base of the tree and decompose into the soil.
  
  

Turf Types

• Avoid Kentucky bluegrass and ryegrasses when seeding for shady areas.Polka Dot Images/Polka Dot/Getty Images
  
  Some issues with growing grass under trees are caused by trying to grow the wrong kind of grass. If the oak tree is not very large and the shade not extremely dense, you should choose a shade-tolerant grass species. Fine leaf fescue types of turf are the most commonly available shade-tolerant grass species. Select a seed mix that contains at least 50 percent of a combination of creeping red fescue, chewing fescue or hard fescue.
  
  

Maintenance

• Raise the mowing height of your mower blade when mowing grass under oak trees.Comstock/Comstock/Getty Images
  
  Grass growing in shade has different cultural requirements than grass growing in full sun. Applying the same fertilizer and mowing regimens to grass growing under trees can often weaken the grass. Do not mow grass that is growing under trees as often or as short as grass in full sun. In general, allow the grass to reach a height of 3 inches or more before mowing and then do not remove more than one-third of the grass at a time. Reduce fertilizer applications in these areas to compensate for the slower growing rates of shade-grown grass.
  
  

Alternatives

• There are hundreds of hosta varieties that will grow under an oak tree.Hemera Technologies/Photos.com/Getty Images
  
  It may be wise to cease trying to grow grass under oak trees and opt for an alternative. Many groundcovers and perennials are adapted to growing in the same type of forest environment that oak trees are used to and that grass finds inhospitable. Hostas, sweet woodruff, bugleweed and barrenwort are just some of the many shade-tolerant plant options for under an oak tree. You can also use a ring of mulch or gravel as well as flagstone or pavers to occupy the space formerly held by your struggling grass.