Perhaps you can pick one of the young branches and gently scrape off a bit of the bark with your nail to see if it's green and supple. If not, then go to a bit older branch and try it again. If it is, then it's just late and hang in there. It may be ok. I have a couple trees just leafing out now...a pecan, a Kentucky coffee tree and an Asian catalpa. Way behind last year on foliage, and that's OK.