Hi!
I just wanted to let you know I think it's fabulous that you're taking an interest in all of the plants the previous owners left behind. I had a beautiful garden at our home in NC (I even won "yard of the month!). When we moved, I took some of my very favorites, but left some very unique and special plants, including all of the George Tabor azaleas that I had propagated. About a year later we went back and drove past the old house. It was all gone. I nearly cried and my old friends thought the new owners were criminal for just ripping out and throwing everything away (not even giving it to the neighbors).
So good for you! And that said, your neighbors might be a good source of information. In lots of neighborhoods and subdivision, folks share their plants by giving away
seeds and cuttings or just extras as teh plants grow beyond their boundaries. So look around. If you have something that looks like one of your neighbors, could be the plants themselves have a parent-child relationship!
Marica