For many plants, root division is an
easy way to make more plants. First, be sure the parent plant is mature
When you divide a plant depends on
when it blooms. Divide:
Spring flowering plants
after they have finished flowering
in the early spring
The day before you are going to divide a plant, water it well -- if
you do it just before digging it up, you'll be working in mud.
Dig up the plant so that you have the entire root ball, and then
gently tease it apart.
Sometimes the root ball can't be pulled
apart. When that happens, pry the roots apart with a trowel or shovel,
or cut them apart with a sharp knife or saw.
Be sure each clump has roughly as many healthy leaves as
healthy roots. Trim off any broken or diseased roots. Trim the tops back
to about a third of the original size.
Replant the new plants where you want them to grow. Set them into the
ground at the same depth as they were before, and water well. For a few
days, protect the transplants from wind and sun, and keep them moist.
Two excellent guides to plant propagation