Herbaceous peonies are just one of the three types of peonies out there. Two relations, intersectional and tree peonies, can be divided in fall like their herbaceous cousins. When it comes to tree peonies, only multistemmed types are divisible. Multistemmed tree peonies send up many shoots, so they can be broken up with a few stems to each division. Single-stem tree peonies have just one woody trunk, which can’t be sliced in half. To divide a tree or intersectional peony, dig it up, put it under a tarp the night before cutting, and replant it after division, with its eyes 2 to 3 inches below the soil surface. The differences, however, crop up in the actual division of the plants. Easy, right? Just be aware of the differences between intersectional and tree peonies when it comes to the actual division process.
Look intersectionals in the eyes before making divides
Intersectional, or Itoh, peonies (named for Toichi Itoh, their original propagator) can be cut apart at the most narrow connections between larger pieces of root, each at least 6 inches long.
Cut the intersectional at a thin point between larger sections, as you would if you wanted just a bit of a large ginger root in the kitchen.
As you visualize the cuts, remember that intersectionals send up new stems every spring, so they have eyes like herbaceous peonies do. Leave at least three eyes on each new division to ensure stems and flowers the following year.
|Make your cuts with an old but sharp knife.||Each division has at least three eyes (pictured, insets) that will become stems and flowers.|
A tree peony is a Gordian knot: one smart cut can get the job done
Tree peonies are woody perennials that bloom on old wood, so there are no eyes to worry about when dividing. They keep stems aboveground year-round, and feature many wiry roots around larger, fatter ones. Only multi-stemmed tree peonies are divisible. They send up many shoots and can be broken up with a few stems to each division. Single-stem tree peonies have just one woody trunk, which really can’t be sliced in half: you could try, but chances are disease or pests will enter the plant through the massive wound you’ve created and kill the peony.
|Multi-stemmed varieties are easy to divide.||Single-stemmed tree peonies should not be propagated by root division.|
Take your time and look carefully at the fatter roots for the simplest cut that will free up new plants. Make sure you get lots of root and a few stems on each division.
|Tree peonies bloom on old wood, so leave the stems intact.|
Make cuts with a pruner at the proper nexus: the spot in the thick root where a slice will let you pull two plants apart. Sometimes, one good cut is enough to divide the peony.
|Find the point or points at which the fewest cuts will free up divisions.|
Snip and pry judiciously, so that each division receives at least 6 inches of fat root to sustain top growth. If you feel that a division lacks enough roots to thrive, cut back some of the woody top growth to ease the strain.
|One cut is sometimes all it takes.||This tree peony has been divided into two.|
Learn to divide herbaceous peonies in Fine Gardening issue #148.