Nandina -DIVIDE AND MOVE?
March is the beginning of the planting and transplanting season for woody landscape plants like Nandina. Transplants should be set into the ground at the same depth as they were in the original planting. It is really up to you as far as how big the divided portions should be. Keep at least 2-3 stems in a clump, at a minimum. You could transplant larger sections if you want groupings that are more substantial.
Please be aware that this is an invasive plant in Maryland. Its berries are toxic to some types of wildlife (birds). It is no longer recommended for home gardens, even though it is still available in garden centers and nurseries. There is more information about Nandina here: http://mdinvasives.org/iotm/feb-2018/