you destroyed something that had the potential of becoming a tree. Not really sure why you want to separate these out into two distinct entities. What would you consider an acron that sprouted a stem and a leaf? A tree or an acron? I think most people would see that an acron is still the same living being, just a different configuration of cells in a transitionary state to becoming a tree.
You are a distinct collection of cells. As opposed to your neighbour, who is also a distinct collection of cells, which is different from you. Every one of your cells is different than his cells, for one, because they all have different DNA than your cell's DNA.
Its fine to claim that you only exist in the present moment. But to deny that your past self also existed for you to exist now, seems a little discontinuous and meta physical.
Also at what time scale does your past self not exist. Since your perceptions are time delayed. You might stub your toe, but it will take a split second for your brain to notice.