Dividing PerennialsPerennials are wonderful plants. They come back each year and each blooms on a reliable schedule all its own, allowing a gardener 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 the entire plant into pieces and replant each piece, either in the same or different locations.
Divide and multiply!
Steps to dividing perennials
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 the gardener to create drifts throughout the bed, or to fill in new beds. Dividing a large clump of one plant can make room in the garden for new and different plants. Dividing is also a great way to share plants with friends and neighbors. And if there are simply too many, divisions can be potted up and sold at yard sales or roadside stands, or donated to a local garden club.
When to divide perennials
Spring is a great time of year to divide summer and autumn flowering perennials, such as Shasta daisy, black-eyed Susan (rudbeckia), and garden phlox. Hostas, daylilies and large sedum such as Autumn Joy or Matrona can be divided as soon as the little noses poke out of the ground in spring. Don't wait too long — divide hostas, daylilies and sedum before they leaf out. Each division will get a head start during the growing season and will reward you with renewed vigor and abundant flowers.
Try not to divide spring flowering perennials in the spring, as you may sacrifice the flowers. Wait to divide plants such as astilbe, iris or peony until after they have finished flowering and the weather has begun to cool, but not later than six weeks before the first frost. Also, try not to divide any plant that has already sent up flower stalks or has flower buds on it. Flowering uses up a lot of the plant's energy, and it may not have the resources to establish a new root system and flower at the same time.
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 will help the plants recover from the stress of dividing and replanting.
How to divide perennials
If you do work in the sunshine, shade the plants with a large cardboard box or plastic container after replanting to prevent wilting. Water each plant to be divided thoroughly and let it soak in while gathering tools. Gather a shovel, spade or spading fork, heavy-duty knife or pruning saw, pruners, a tarp or old tablecloth, water and mulch. If you have compost or other organic matter, use it to mix into the soil that is used to replant the divisions.
Choose locations for the new plants and dig the planting holes before dividing 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. Loosen the soil around the sides and bottom of the planting hole.
Divide large, established, healthy plants. Use a shovel or spading fork to dig deeply all the way around the entire 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 before you lift 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 will not be harmed by cutting them with a knife or shovel.
Gently lift the plant out of 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. If the divisions are smaller, they should still grow well, but may take longer to establish themselves and flower at their maximum potential.
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.
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 into their new holes their original depth, not deeper. If the planting hole is too deep, remove the plant, add more soil/compost mixture and tamp lightly before setting the plant in. Plant one division back into the original hole. Fill in around the plant with soil/compost mixture and tamp down lightly.
Water each division thoroughly. After the soil has dried some, you may need to add a bit more soil/compost mixture to make up for sinking soil. Water again, then lay an inch or two of mulch to keep 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 until your new plants become established. Wait a few weeks for the plant to start actively growing again before adding fertilizer.
Be sure to replant divided perennials promptly so roots don't dry out. If the new plants can not go into the ground immediately, plant them in pots, water thoroughly and set them in a shady area until ready to go into the ground.
Dividing a plant multiplies it and adds to the joy of gardening.