Plants that pop up in the garden from seemingly nowhere are referred to as volunteers. These may arise from seeds cast off by plants in the garden, from seeds consumed by animals that survive their digestive system, from squirrels burying their various treasures, or other sources.
I had noticed a number of juvenile volunteer plants that I wanted to collect for other purposes so I did just that today. I found young plants that showed up in random locations and transferred them to pots. I ended up with two laurels, two holly plants, two big leaf maples, and five tiny vine maples. I have some ideas about where these might go in the future, but in the meantime I’ll tend them so they can grow healthy root systems.