Perennials give clues when its time to divide, replant
from Tulsa World
Pampas grass is a perennial, a class of plants in which the tops die back in winter but re-emerge from roots in spring. A general rule of thumb for dividing and replanting perennials is that it depends on the time of blooming. For those blooming in spring, fall division may be best, and for those blooming in summer and fall, divide in spring or after fall blooming is completed.
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