We planted some pampass grass in April but one of the plants didn't grow. We now want to split off one of the successful plants into that vacant spot. Can we do this now or do we wait until the spring? Or, should we just plant a new plant in that spot, hoping it will catch up to the others in height?

(I searched and found information based upon fall or summer grasses but I don't know into which of those categories pampass grass would fall.)