I see these same plants in yards all over Atlanta. I don't know if they're trees, small ground plants or what. Can someone please help? Thank you!

Plant 1:



Plant 2:





Plant 3





Plant 4:

Plant 1 appears to be a Violet of some sort.

Plant 2 is Common Threeseed Mercury (Acalypha virginica var. rhomboidea) .

Plant 3 is a Common Hackberry (Celtis occidentalis) seedling.

I think Plant 4 is an Elm seedling, but the last picture in particular looks like it might be another hackberry instead.

I think plants 3 &4 are both hackberry.