In terms of the numbers sold and planted each year, the daylily is probably America’s most popular perennial. One of the quickest and easiest ways to obtain more plants (or to restore the floriferousness of an overgrown clump) is by division of a mature plant—one of the most basic horticultural skills, and one that every serious gardener should have under his or her belt.
You may want to divide a daylily because you want to increase a new, expensive variety, or simply because you have a reliable performer in a color you like and you want more of it in the border. Whatever the reason, make sure the plant to be divided is healthy and has multiple growths that will yield good-size divisions. The best times to divide daylilies are late spring, after the soil has warmed, and fall, preferably at least two weeks before the first anticipated frost.
One of the other benefits of learning this techinque is that it can be applied to other clump-forming perennials such as hostas, border phlox, and asters (asters, however, should be divided only in the spring).
1. Dig up the clump with a garden fork, taking care to keep the root system as intact as possible. With a pair of pruners, cut back the foliage to about 6 to 8 inches. Use a hose to wash most of the soil from the roots.
2. Examine the clump to see how many divisions you can reasonably get. The smallest possible unit is a single “fan” of foliage. Divisions consisting of more than one fan will produce fuller plants. If the clump was large to begin with, the divisions can often simply be pulled apart; if they don’t separate easily, use your pruners to cut the divisions apart.
3. Carefully separate the divisions. Whatever their size, make sure that each one has a reasonable number of roots; otherwise, the plants will take a very long time to recover.
4. Replant the divisions in well-prepared soil. Make sure the hole is big enough so that you can spread the roots out-you shouldn’t have to bend or twist them. And don’t plant too deeply-there should be only about an inch or two of soil above the point where the roots emerge. Firm the soil and water in well. A two-inch layer of mulch will help the soil retain moisture.