Planted itself in a pot that was knocking around. Somebody gave me a pot plant that died and I dumped it outside intending to empty it, but never got around to it. This has been growing in the pot at least two years (yes I'm a gardening slattern) and is definitely not the original plant, which was something bushy and purple daisy-like. This is some sort of shrub, I think. Multiple stems, so not a tree. Any ideas?