We divide plants for two main reasons. First is to rejuvenate. As some plants grow older, they bloom less and are less vigorous. Dividing rejuvenates them. Second reason is to get more plants! If you love the plants you have, why buy more when you can make more? Fall is the ideal time to divide perennials. The cooler weather and the gradual fade to dormancy puts considerably less stress on plants. This is a good thing, because digging up and dividing plants can stress them out.
Photography by Joy Yagid.
Before you start digging up plants to divide, remember that not every plant can be divided—and of those that can be divided, fall may not be the best time to do it. In addition, how you divide them matters. Technique varies depending on the type of root system each plant has. Plants can have traditional roots (like black-eyed Susans), fibrous clumps (like ostrich ferns), rhizomes (like hostas), crowns (like Joe Pye weed), or tubers (like daylilies).
What You’ll Need
Once you know what can be divided and how, you need to make sure you have the proper tools. Beyond a good pair of garden gloves to protect your hands and maybe a tarp to contain the soil, you will need a garden spade or shovel, a spading fork (or two if you have a big job), a pair of pruners, and either a trowel or a hori hori knife (see Tools of the Trade: Japanese Garden Tools). The hori hori can do double duty as both a trowel and a knife and is the reason I prefer it. One less tool to carry.
A few large empty nursery pots will make it easier to move the divided plants around or to hold them for a few days until you decide what to do with them. Don’t let them dry out if you’re not replanting immediately. When you do replant, give them the best start by digging a hole one and a half to two times the size of the roots, back fill with good quality garden soil, and water deeply.
