leaf

I'm having trouble identifying this tree at the rear of my property, in Miami, Florida. Nobody seems to know what it is and I'm afraid it could be of the poisonous type... Does it look familiar to anybody?

We bought this tree in April 2017 (its now 8-31-17) and planted it the same day. Im attempting to find why its struggling. The symptoms are dry leaves - some of which are turning brown, but do not fall off on their own. The leaves are all very small (appx 2-3 inches at the most). The leaves are...