White mulberry lost leaves in spring

Hope someone can offer some advice...I had a couple of tallish white mulberry saplings in large tubes in a polyhouse, where they warmed up early spring.....then i transferred them outside and unfortunately there was a bit of cold weather....now all the healthy new leaves it had grown have fallen off and the weather's quite warm.  
Will they survive?  Should I trim them? How far?

It will set the plant back since it used up the stored nutrients to grow the buds then it loses significant amount to do photosynthesis. If the apical bud isn't killed it will continue to grow otherwise secondary buds should form shortly to grow new leaves. There's no need to prune and stress the plant even more.