Let nature take it's course or prune all back to same size. Even then there is no guarantee that any of them will be the same size even if you had planted them in a row. Plants and people grow at their own rate.

You can cut or pinch the candles back each spring on the larger trees for a few years until the smaller trees catch up, but I'm not sure that's really necessary. As the trees grow, their relative differences will become less and less, so, in the long run, I don't think the extra work is really necessary.

Thanks guys.....I can see a decrease in size gap in some of the trees that were planted closer together in time. But the ones that have a 2-3 year gap are way behind. Any fertilization I can do to help even a little? I don't want to inhibit growth of the larger ones.

Since they will all grow really large in time, I'd just let them be. You may even discover you need to offset them a few feet (alternate every other one forward a little, back a little)rather than have them in a straight line. That is one thing about gardening-you have to be patient, but it is almost always worth it in the end. If not, you can always change it. It looks like you are trying to screen the road and a couple of deciduous trees (anything you like-flowering or not)could also be interspersed with the evergreens-again, not in a straight line, but they might grow more quickly and then the small blues won't bother you as much. I know this is way more than you asked for, but your photos got me envisioning what I would do. Of course, when I begin to do that here at home DH just zones out! Feel free to do the same!!

Fertilizing trees only helps if your soil has a nutrient deficiency. If you add more of some nutrients than your trees need, it can actually negatively impact them.

So, if your soil is not short on nutrients, then fertilizing won't help. If you soil is short on nutrients, then fertilizing only the smaller ones will be "inhibit(ing) growth of the larger ones."

It seems to me like you'll have to make a decision as to whether you prefer maximum growth rates with differing sizes of trees (at least for a while), or, similar sized trees accomplished by "inhibit(ing) growth of the larger ones" one way or another.

Trees frequently exhibit transplant shock when first tranplanted. This means it may take a couple of years for some of the trees to get their roots in a condition ready to support healthy top growth. Once this happens, I thinkthe grow rates will even out. However, the ones in the shade might never grow as fast as the ones in the sun.