here are you .... big city name ... sun in MN isnt the same as FL sun ...

how did you plant it ... amend planting hole.. was it BB or potted.. did you do root surgery at planting due to winding roots ...

did you amend the soil ... how did you water it in.. what is your native soil ... etc ...

you really havent given us anything to work with here ..

two things to keep in mind.. the only problem with full sun .. and white tissue is your plant will burn the white tissue in too much sun ... especially if you cant or dont give it enough water ... and you dont mention burning.. so sun is probably not the issue.. but i dont know where you are. ..

and... trees can take 2 to 4 years to really get growing with vigor ... as they need to grow or re-establish the root mass ... and the problem here.. is all that growth is where you cant see it ... and i hope you arent relying on lawn irrigation to properly water a transplanted tree ....

but since i dont know any of the info above.. i cant speculate further on that ..

bottom line... with some trees.. you just have to be patient.. and with plants that can live multiple decades ... 3 years isnt all that much time ...

ken