Question
I manage a mid sized lawn care operation in Scarborough, Maine.  We maintain a variety of types of properties and have had some clients for decades.  Many of these lawns improve under our care but several seem to be decreasing in quality.  The common denominator with the decreasing lawns is heavy shade and oak trees.  Even my own lawn, established in 1875, is showing areas of serious sparsity in areas of shade that never had a problem until the last couple years.  I suspect our machines are causing some problems in these shaded areas.  We switched to an ATV type tire for our Walker mowers.  The tires are wide and have widely spaced lugs for traction.  I figure this makes a smaller contact patch and causes compaction under these lugs or at least small spots of soil disruption damaging the tender roots of shade grasses.  This damage may be small but over months and years couldn't this cause serious thinning of grass?  All these lawns show the first signs of thinning around beds in a circle pattern even though we go very slow around beds.  Also, the weight of the machines pushes acorns into the ground until we do fall clean-up when many but not all acorns get raked up and out of the turf.  More root damage?
What practices of renovation and maintenance would restore these shaded lawns to decent quality?  My boss always says "We could cut down all the trees" or "you can have alot of trees or a lawn but not both".  Can't grass exist and even thrive in such conditions with the right practices?
Thank you for any help provided.
Tom Wakem  

Answer
Growing a dense lush strand of grass under mature oak trees can be challenging. Generally, I recommend using fine fescues (or tall fescue, if this is in the rest of the lawn) and mow the lawn high (3.0-3.5"). Fertilize once or twice in fall, only. I like to overseed the area once or twice per year (spring and/or fall), with emphasiz on spring.

Core aerating every september is also recommended.

It is not uncommon for lawns to deteriorate progressively over the years. Follow up by regular core aerating, moderate fertility, and annual overseedings can keep a good result.