St. Augustine grass mixed in with Bermuda grass?

If your lawn looks like this then you know just how hard it can be to get the thick, green, uniform, and weed free lawn you desire. This is because you have St. Augustine grass and Bermuda grass all mixed together. Sometimes St. Augustine will creep into Bermuda lawns if there is St. Augustine in part of the lawn or part of a neighbors lawn. Vice versa, Bermuda grass can creep into a St. Augusinte lawn in the same way.

Why is this a problem?

The reason a St. Augustine / Bermuda mix is a bad thing is because the two grasses preform differently under different conditions. As such, caring for one can damage the other. For example, Bermuda should be cut at 1 to 2 inches but St. Augustine should be cut at 2 to 3 inches. Bermuda performs better in full sun but St. Augustine does better in shade. Some weed killers that control grassy weeds can be applied in Bermuda lawns but if they are applied in St. Augustine lawns they will cause damage. Long story short, it is a very difficult problem to have because there is no easy solution.

What is the best solution to a St. Augustine/Bermuda mix?

There is no 100% right answer to this questions but one good solution is to decide which grass your lawn conditions favor. For example, if you are in full sun and have more Bermuda grass than St. Augustine it makes sense to practice techniques that will favor Bermuda grass. If this is the case you can cut the lawn at 1 inch and apply herbicides that are know to stress the St. Augustine. Also, over-seed with Bermuda grass seed in the summertime. Following this strategy your goal will be to slowly stress the St. Augustine with the aim of crowding it out over time. If, on the other hand, you have shade conditions and can see that the St. Augustine is the primary grass type then you should perform techniques favorable to St. Augustine. This would include cutting higher (2.5 to 3 inches), fertilizing with less nitrogen and avoiding herbicides that can damage the St. Augustine. This strategy will allow the St. Augusitne to slowly take over the lawn and crowd out the Bermuda.
St. Augustine Lawn with Bermuda Creeping In: