How to Divide and Rejuvenate Perennials

Dividing is nothing more than digging up a flower, cutting it up into pieces then replanting it. Timing is everything, and it's simple to remember when to do it.

If the plant blooms in the spring or the summer, wait until fall to divide it so you don't rob the plants of its flowers. If it blooms in the fall (like Rudbeckia, then wait until spring to divide it.

Some of the best perennials to divide in the spring include:
asters
blanket flower
chrysanthemum
sedum

In the fall, you can divide:
peonies
bearded iris
astilbe
hosta
yarrow
daylilies

The process for dividing is pretty much the same for all of the flowers. A couple of days before dividing, water the plants well. This will help with the transfer and also helps eliminate a lot of the stress.

A couple other tips to keep in mind: for fall division, plants need about four to six weeks to get established before the ground freezes, so divide early in the season. If you're dividing in the spring, do it as the plants emerge from the ground during cool weather and don't wait until the heat sets in.

Other perennials have spreading root systems, which means sometimes you can just pull them apart. Hostas are a great example of a perennial that can be divided by just tugging on the roots and pulling them apart.

For plants like bearded iris, which grow from rhizomes, use a knife to divide them.

Keep your new perennial watered well. When the ground freezes hard in the fall, put a thick layer of mulch around it to help it through the winter. In the spring, pull mulch away the mulch to allow soil temperatures to warm up.