One of my developing interests is in bonsai cultivation, which is a long-term venture in which trees or shrubs are either grown from seed, or to speed up the process, collected from "the wild" so as to find a specimen that already has the desired trunk thickness.
I have identified several plants with potential to become bonsai. A privet hedge I planted at my rental property about 10 years ago has been slowly dying because of its proximity to a black walnut tree (which is poisonous to many other plants) There were two left still alive, but suffering, so I dug them up and put them in pots. I've been watching them all summer and they seem to be rebounding, so by next Spring I'll probably choose just one to begin training by cutting off the tap root, and any branches that don't fit into the design I decide on.
In May I was working in a national cemetery where they happened to be digging out a row of Yew bushes, so (with permission) I salvaged one from the trash heap and brought it home. I'm afraid it might be dying, but I'll wait until Spring to see whether it grows any new leaves. You can see the Yew in the picture to the right of the glider. The two privets are in a pot and a bucket to the left of the glider.
The third possibility is an American Elm tree I noticed in my parents woods. It has a nice gnarly trunk base, so with permission, I cut back the height of the tree to about 1/3, and pruned the roots to about a 14" circle. Next Spring I'll dig it up and pot it. I don't have a good picture yet.