Most tree guys I know and network with would tell you that turf growing under you trees is horrible. I don’t agree with this. There are definitely some potential problems. But, in my opinion, the potential benefits out-weigh the potential problems. Growing turf grass around trees can be done successfully. But, be careful.
There are three basic arguments against turf growing under trees. The first is that the turf robs all the nutrients in the soil. Ok, yes, grass chews up a LOT of nitrogen. But, if you are mulching your clippings and not bagging then most of the nutrients are staying there. And, most people are good about providing supplemental fertilizers. Just make sure the fertilizer you use doesn’t have weed killer mixed in. We call these products weed-n-feeds and they are HORRIBLE for trees.
The next argument against turf is that you have to over prune the tree to thin its canopy to allow enough light through for the grass. This is basically bad advice and should never be done. St. Augustine will survive under a properly pruned tree (without excessive thinning). No other type of turf is going to survive under a fully shaded yard regardless how much you thin the trees.
The third argument goes back to the fertilizer topic: risk of herbicides being applied to the trees. Most of the big-box stores really push these products. If you walk in the front door of a major do-it-yourself store in the spring, you are likely to find weed-n-feeds front and center and on sale. This is the only legitimate argument in my opinion. Weed-n-feeds kill a lot of trees every year.
So, to me, the one really big argument FOR turf is…irrigation. Most people won’t watch the trees really closely, and even when they do, they don’t know how to recognize drought stress in trees and therefore won’t water. But the grass is a different story. Bringing grass into the landscape means that you WILL be watering more, or your grass will be dying. This addition of supplemental irrigation is really great for the trees. It will even overcome many of the incidental stresses inflicted to trees by landscaping.