Q.Bottle Brush Tree
I noticed a side of the tree was loosing its leaves. At a closer look I noticed the bark on the tree trunk was splitting open. The tree is about 12 / 15 feet tall. I feel like the bark splitting is the under lying cause, but do not know what or how I should treat this. There are three main trunks on the tree. Two of these have the problem. The tree loosing its leaves has just happened in the last few days, but is progressing rapidly.
If your bottlebrush is producing new growth and looks otherwise healthy, I don't think the bark splitting is anything to worry about. The bark tends to produce fissures as it ages, especially on the side that receive winter sunshine. The bark then dries out and looks shaggy, but the wood is sound. I don't think splintering bark should cause concern.