Pruning oak trees

[Jetblack3]

Purchased an acerage approximately 15 years ago, built a new home and began planting hardwood oaks. Have mostly swamp whites and reds with a few pins. These were all nursery trees with approximately 2 inch trunks when planted and probably 10 feet tall. Currently I have 20 living oaks and the earliest ones have better than 6 inch trunks and are over 20 feet tall now. Others are nearly 4 inch trunks and near 20 feet tall. I've pruned them a little every winter (Iowa) mostly cutting to bottom limbs off to give me riding mower clearance under them. I have a few trees that have a couple larger lower limbs that I left alone because I felt like they were too big to lop off. Max size might be an inch to inch and half. Is there a standard limit on size to be pruning off ?
Also since I'm on a large hill some of the trees are really reaching to the east/ north east where they get a good dose of morning sun. Is it OK to lop off those reachers to give the tree back its shape

 

[buzz sawyer]

I'm no expert on pruning but what is your long-term plan for them - looks, lumber, firewood?

 

[Jetblack3]

Their yard trees, but would just like to mow under them without leaning over the side or ducking to clear them when passing under. Trees are on a steep hill so on one side the limbs may be as little as 3-4 feet from ground and 5-6 on the other. Just basically want to know if there is a cutoff on size to prune

 

[Oldmaple]

Some pruning recommendations. The smaller the better since the wound closes over faster. Don't remove the lower limbs too early since it will lessen the trunk taper (I know, it contradicts the first recommendation). This will make it weaker in the future. I like the 1/3, 2/3 rule, meaning maximum 1/3 trunk, 2/3 canopy when you step away and look at it. This is more for aesthetics for me but also gives a starting point for the taper part.

 

[buzz sawyer]

How close to them do you mow and with what? Be careful not to compress the soil and damage the roots. Do you have a mulch ring?

 

[Jetblack3]

small mulch ring around them, some more than others. They get a wheel barrow of mulch each spring when I remove the old from the wifes flowerbeds. Weed eat every other mowing. Mow with a front mount 72" grasshopper