I planted 10 gallon Purple Robe Locust approx 3 years ago (was probably 12' tall at the time); and now it's grown to about 16' high and looks very healthy. However, I noticed yesterday while watering it - that it has about a 9" Vertical crack all the way through the bark to the wood of the tree. This crack starts about 10" up from the ground & has separated the bark completely from the tree approx 1 1/2" on either side of the bark split--leaving a gaping hole to the wood. I've never seen this? I will say the tree has certainly grown the most this Spring/and looks healthier than it ever has... but I'm worried that if I don't treat the crack it may well kill the tree? Any Suggestions?