The first 2 pics are from the KCT that will need the most pruning. 3rd pic is from KCT that has good form so far. Last one is actually from an elm planted last summer in the park (with permission) but has lots of branches curling downward and not sure when I should cut them off.

How long have they been growing in that spot, Krissamn?

I would not worry about trauma or setting the trees back from pruning, they all look like they are growing well. Take out branches that have to tight an angle to the main trunk of the trees and any that may be growing to the center or towards another branch that you wish to keep. I cut back branches that I want to bulk up the branch and to redirect growth.

Seed grown KCT will be the species with any of its potential variations, and not an exact, genetic duplicate of the parent. To make a duplicate, you'd need to vegetatively propagate a piece of original parent tissue.

To prune for a single leader trunk (one which does not branch until the canopy, remove lower limbs/branches back to the main trunk, up to 50% of the tree's total height, once per year, preferably prior to new Spring growth. If you missed that "best" time, calculate how it was then and remove the same limbs/branches. Do this only once per year in order to give the tree an opportunity to restore energy to the roots prior to the next cutting. (You can remove a minor branch here or there at other times without consequence.)

There are a couple of reason why to remove the lower branches as opposed to letting them do and doing it much later.

1. Removed when young, the cut is minor and heals quickly
2. Some lower limbs will take a skyward turn and quickly begin competing with the central lead, as secondary one. In doing this they will develop their own section of canopy. Removing them later can take a big chunk out of the overall canopy, disfiguring it and making recovery long, or impossible, depending on the degree of severity.
3. Removing the branch as soon as possible works toward regaining the ground space below the tree for human activities.
4. Removing growth causes a spurt of growth as the tree's roots try to re-balance the root/canopy-energy equation. In spite of the growth removed coming from the bottom of the canopy, the growth returning on account of it will most likely be in the upper portion of the tree. Thus, the tree grows taller, faster.

If one removes lower branching and foliage just prior the beginning of Spring growth -- to a 50% trunk/50% canopy proportion -- the tree will have the entire season to put on new growth. What starts as a 50/50 proportion will end the season more like 60% canopy to 40% trunk, which is a handsome proportion for a tree to have through the remainder of the year. Since the Spring growth is sudden and rapid, it is very little time before the tree regains a 60% canopy.

Obviously, as the tree grows over the years, there comes a time when the permanent bottom of the canopy has been reached and there is no longer a need to keep raising it. Then the tree is free to grow as high as its genetics will allow while every year gaining a greater portion of canopy relative to trunk height.

Indianagardengirl, they sprouted in the lawn last spring.

Thanks for all the input Yardvaark. I will prune them tomorrow. One has a strong leader that branched lower and has now overtaken the lead. should I cut that one off, back, or let it take the lead and cut back the original leader?