Proper time of the year to trim Eastern White Pine
I live just outside Milwaukee, WI and I have 2 Eastern White Pines that were planted 5 years ago. They are now appox. 20' tall and doing great. However, I would like to start pruning up the lower branches (they go all the way to the ground) since they are getting fairly long (longer than the 6' diameter wood chipped ring). What month is a good to start pruning off the lower branches? Ideally I would like 5-6' of clearance from the ground for now.