Haven't mowed the lawn in a few weeks since it's been so hot. These things are sprouting up in one area of the yard. I've seen them in the past but always just mowed them down with the grass.

This time I dug down to have a look and they are shooting up from roots underground. Roots are about 1" in diameter and about 8" below ground. There used to be a old red or pink crepe myrtle in the area, which I had to cut down (stump was removed too) about 4 years ago to re-grade the yard.

These things are only coming up in this area of the yard.

If they are baby crepe myrtles, attached underground, is there any chance to cut them from the old roots and transplant them elsewhere? Anyone have any ideas about that?

Or, are these just some strange looking weeds I should roundup/mow?

Picture shows how it looks above ground, and also the view dug out connected to a root. (in this case, the end of a root)