What's Up Magazines

Dividing Perennials in Fall
Prepare for Winter and Share the Bounty of Your Garden.
By Lori Pelkowski

I got tired of my perennial garden this year. It was too lush, to the point of looking sloppy and overgrown, even though I took great pains trying to keep it lovely and weed free. So I decided that my dear friend, who had mentioned that she was building a new bed in her already glorious garden, needed at least half of my plants, especially the ones that grow with wild abandon. After all, she needed to have that new garden bed filled and flowering by next spring. So I got out my tools and dug in. In a few hours, I had the back of a pickup truck filled with spring- and summer-blooming perennials?foliage, roots, soil, weeds (yes, I admit it), and bugs. When I delivered the plants, I told my startled and overwhelmed friend that all she had to do to repay me was to give me back my wayward earthworms.

I may complain, but perennials really are wonderful plants. They come back every year, and each one blooms on a reliable schedule all its own, allowing you to mix and match colors, textures, and bloom times. As perennials make themselves comfortable in a garden over the course of as little as two growing seasons, they may need to be divided. Dividing a perennial means to cut it into pieces and replant each piece, in either the same or different locations.

Blanket Flower

Perennial plants can be divided for many reasons. Competition and overcrowding can weaken a plant and prevent it from blooming to its full potential. Dividing a beloved plant allows you to create drifts throughout the bed and helps fill in new beds. Dividing is also a great way to share plants with friends and neighbors, whether they really want them or not. And if there are simply too many, divisions can be sold at yard sales and roadside stands or donated to a local garden club.

Fall is a great time of year to divide spring and summer flowering perennials, such as daylily, bee balm, bearded or Siberian iris, peony, astilbe, poppy, or daisy. [Some perennials that bloom in late summer, such as black-eyed Susan, chrysanthemum, and aster, also benefit from dividing in fall. Each division will get a head start over the winter and reward you with renewed vigor in the spring.

Choose a cool, cloudy or overcast day to divide and replant, just before a rainy spell is predicted if possible. Cool temperatures and gentle moisture help the plants recover from the stress of dividing and replanting. If you do work in the sunshine, shade the plants with a large cardboard box or plastic container after replanting to prevent wilting. Thoroughly water each plant to be divided and let the water soak in while you gather your tools. Gather a shovel, spade or spading fork, heavy-duty knife or pruning saw, pruners, tarp or old tablecloth, water, and mulch. If you have compost or other organic matter, use it to mix into the soil in which you replant the divisions.

Try to select locations for the new plants and dig the planting holes before you divide the original clump. This will minimize the time the plants spend with their roots exposed. Dig the hole slightly wider than the division will be to allow space for the new plant to spread out its roots.

Perennial Plants to Divide in the Fall Hosta Aster Astilbe Bee balm Black-eyed Susan Blanket flower Chrysanthemum Coral bells Daisy Daylily Hosta Iris Peony Poppy

Divide large, established, healthy plants. Use a shovel or spading fork to dig deeply all the way around the plant. Keep as much of the root system intact as possible. If working with a very large clump, force the shovel under the root-ball to loosen it before you lift the plant. Or insert a spading fork, at an angle, several inches outside the perimeter of the top growth. Work all around the plant, lifting gently until the clump comes free from the soil. A spading fork won't damage roots as much as a shovel, but certain plants with very tough roots, such as daylilies, will not be harmed if they are cut with a shovel.

Gently lift the plant out of the ground. Shake off loose soil and wash the crown with a garden hose if the roots and crowns are not clearly visible. Each division should have two to five strong shoots with ample roots attached. Set the plant down on a tarp or old tablecloth on a flat surface and divide it into smaller clumps, either by hand or with a knife or spade. Roots of older or woody clumps can be so tough that you'll need to cut them with a heavy-duty knife or split them with a sharp spade. Plants like hosta and coral bells can have very thick, dense crowns. If you feel strong and ambitious, split them with an ax once they are out of the ground?they can take it.

Remove any dead, damaged, or diseased areas of the plant. If the foliage is too lush to be supported by the new root-ball, cut the leaves back to half the height of the original clump. Set plants out at their original depth. Planting too deeply can invite crown rot, while not planting deeply enough can cause the plant to heave out of the ground and die over the winter. You can plant one division back into the original hole. Fill in around the plant with a mixture of soil and compost and tamp down lightly.

Water each division thoroughly. After the soil has dried some, lay an inch or two of mulch to keep the soil from drying out and to protect the plant's root system. Use shredded leaves, wood chips, or small evergreen boughs. Keep the soil moist for a few weeks until your new plant becomes established. Wait until spring before adding fertilizer.

Be sure to replant divided perennials promptly so their roots don't dry out. If the new plants cannot go into the ground immediately, plant them in pots, water thoroughly, and set them in a shady area until they are ready to go into the ground. If you must leave the plants in the pots over the winter, bury the pots up to the soil line to protect the roots. The divisions should return in spring, ready for their new homes.

Coral Bells

Fall is also a great time to rearrange the plants in a garden bed. If over the course of the growing season flower colors clashed, a delicate plant got lost in a sea of aggressive plants, or short plants found their way to the back of the border while tall plants took front and center stage, now is the time to correct these anomalies. Simply remove and replant the offending plants without dividing them. As gardeners we get to choose what grows where.

If, like my dear friend, you receive plants from another gardener, check them well for weeds and for pests like slugs, grubs, and aphids. Do this after your friend has gone home. And feel free to keep any stowaway earthworms.

Lori Pelkowski is a freelance writer and professional gardener.