If I do have to do some revision to my barrier, I do think I will have
a little time. Each transplant has at least one new healthy culm shooting
skyward, and they will probably really jump in this Georgia heat, but I
probably will have at least a year or two before rhizomes make it to the
perimeter.

Thanks in advance for any advice, FM

By year 3 in your area in decent soil and rainfall expect the rhizomes
to run a distance equal to culm height.

45-60 mil barrier is what you need weedblock isn't going to do it.