While many good quality perennials seem expensive in the garden center, the cost can easily be justified by a patient gardener who divides his or her perennials. Not only does this increase the number of plants in your garden, it’s also good for the plant, encouraging new root growth and better blooms the following season.
Spring is an excellent time to divide many perennials, but fall is also a good time because the warm soil, increased likelihood of rain, and fewer insect and disease related problems combine to make perfect growing conditions for your new divisions. These divisions, supplemented with new perennials, can be used to create a new bed or to extend an existing garden. This allows you to expand your gardens inexpensively and carry a common theme throughout your landscape.
Possibly the easiest perennial to divide, daylilies can often be divided the year after they are first planted or in many cases, right from the pot. They can be divided anytime of the year as long as you cut the foliage back to about 5 inches. The best times are in early spring as soon as they start new growth, after blooming, or in the fall.
Using a good quality shovel, dig up the clump, shake off the dirt, and carefully break the clump apart (a minimum of 2 fans should ensure blooms the following season). Sometimes a knife is needed to break the fans apart, but try to avoid cutting through the crown; insert the knife and use a twisting motion to separate the fans. Replant the divisions in well amended garden soil.
Splitting these beautiful foliage plants is often intimidating to gardeners that are new to dividing. They are actually very easy to divide and quickly recover to their previous splendor. There are several different ways to divide hosta, depending on the particular plant. Sometimes individual plants are far enough apart to simply stick a shovel between them, dig up the piece you would like to move, cut the foliage back, and replant it, leaving the remaining portion in the ground relatively undisturbed. If your hosta is very old and the crowns have fused into a large mass, it will be easier for you to dig the entire mass up, cut the foliage back so you can see where individual plants are, and divide it using a knife or small hatchet.
This is one plant that really benefits from being divided on a regular basis. Old undivided iris are more prone to disease, insect damage, and root rot. Iris must be divided in the late summer after they have stored energy in their rhizomes all summer. To divide iris, loosen the soil with a digging fork and carefully remove the rhizomes. Break the rhizomes apart at the joints where they will snap naturally in your hands. Break off and discard the old, withered rhizomes and any mushy (rotten) root pieces. Then trim the foliage to about 6 inches with a sharp blade, dip the rhizomes in a solution of 1 part Clorox to 9 parts water, and let dry. Replant in a shallow trench spreading the roots out.
More detailed instructions for dividing tall bearded iris
Older established peonies may need to be divided if they are no longer blooming well. The best time to divide peonies is in September or October. After cutting the stems back, carefully dig around and under the plant keeping as much of the root system as possible. Gently remove the dirt from around the roots (sometimes it's easier to wash the dirt away with a hose). Cut the clump into divisions with at least 3-5 eyes (buds) each and a good root system. Replant in full sun with the eyes 1"-2" below the soil surface.
More detailed instructions for dividing peonies
Dividing your perennials is a rewarding process that allows you to justify buying that pricey hosta or daylily you have been eyeing for years. The best way to learn how to divide your plants is dive in and just do it! Check our lecture schedule for Mark Viette’s Propagation Workshops (usually offered in spring and fall of each year); an excellent hands-on way to explore many techniques and learn the secrets to successful propagation. Not only will you walk away with the knowledge of how to divide your own plants but you will also take away a bag full of plants divided straight out of the Viette gardens.