...underneath it is what's really weird. It's the brightest yellow wood I've ever seen.
Good luck killing them. I had one in my last back yard that required attention about 6 times a year to keep it mostly in check. Here was the routine we developed, whichever worked well for both of us:
1. Chop it down to the ground each spring.
2. Spray it with Round Up (a minor irritant to Nandina) about every other month to keep it from growing over the house before Spring.
3. Finally we moved.
Have you noticed the leaves to reduce at all? Also, since they grow with 5 leaves per stem,
I've been cutting the furthest 3 off whenever possible to compact the foliage. Any experience with such treatment?