I just planted two fruiting mulberries. I have a mulberry already that I'm growing in a bush from. These two fruiting mulberries are going to double a shade trees. I'm used to growing small fruiting trees but have never grown a large mulberry before. I've been told that in Arizona its not uncommon for a mulberry to grow ten plus feet its first year. Of this I have no doubt. The mulberry bush in my yard is a beast that must be pruned back three times a year.

So now to my question......

If I let these two trees grow. Pruning with only thinning cuts the first year and the new branches from this 1" diameter 5' tall branchless whip grow 10'-18'. Will the branches be strong enough to withstand the test of time? Or should I be using heading cuts every 2'-3' to slow down the rate of growth and strengthen the branches?