Help...what is this?
I bought 3 dormant plumeria in Hawaii in April, brought them home to Oregon and put them in my greenhouse. All 3 thrived and flowered - I was thrilled! It started getting cold and although my greenhouse is heated, when the temp dropped into the twenties, I brought them inside. 2 of the plumeria are dropping their leaves and going back into dormancy. This one is doing the same, but also suffered from black tip (which I cut off) and this spot on its trunk. It's hard, dry, slowly spreading, and notice the cracks in the trunk around it. It doesn't smell and I can't identify on any sites. Can anyone educate this amateur on what this is?