Mulch as much of the area as you can obviously if your yard is 25 ft across and the tree goes into your neighbors yard they probly wouldn't appreciate it too much if you went to the drip line. Every inch you mulch it makes that less of competition for water and nutrients. So if 4 ft is all that is feasable, Just Do It. (hopefully I don't have to pay to say that)

My dad is from your neck of the woods. I have some other family that still lives up that way.

 

I agree, do as big of an area as you can. If cost is an issue you can use a cheap mulch (chips from a tree service company) underneath and then topdress it with a thin layer of nice looking material.

 

Thanks for all the replies.

Cost is not really the issue here. There are lot of large trees in the yard and they are about 40 feet apart. So a couple of the 20" tree rings close together will probably destroy the landscape.

 

keep the mulch off of the root flare. 4ft is better than none and will protect the tree from mower or wacker dammage. mulch is used in dry conditions to help retain moisture but most just like the look. it would be a good idea to airate and feed the trees with some organic fert . i like to use dry-roots 3x per year. trees roots can grow 3x past the drip line.

 

Obviously I'm not looking at the yard so this may not work but in a lot of landscapes if you have turf with trees in it it would look a funny with a bunch of round mulch areas around them. Often times you can combine the mulch of two or more trees into one larger mulch bed. Put some curves in it, use some large river rock for edging, put in some perennial shrubs and make something out the mulched area that benefits the trees and adds interest to the landscape at the same time.