When Is the Best Time of Year to Divide Perennials?
Avoid transplanting anything during summer or if it’s really hot; it’s stressful for the plants, says Barshaw. It’s best to divide perennials in spring when they’re just starting to emerge, or in fall, when temperatures are not as extreme and rainfall generally is plentiful. The latest you should transplant in the fall is about six weeks before the ground freezes in your area so that plants have time to settle in and get established before winter.
How Can I Tell if My Perennials Need To Be Divided?
Reduced flower power is a big indicator that your plants need more room, says Barshaw. That’s especially true of daylilies and irises. For example, irises tend to appear to die back and not bloom in the center of a cluster when they need more space. You should also divide if your plants aren’t performing well because the growing conditions have changed—such as sun-loving daylilies that are now completely shaded by a tree that has matured.
What Kinds of Perennials Can I Divide?
Most perennials are fair game, but the ones that are easy to divide include daylilies, bearded irises, Siberian irises, alliums, hostas, lamium, peonies, perennial geraniums, sedums, mums and ferns. Types that don’t do so great are those that have deep tap roots such as baptisia, lupines and milkweed, or shrubby perennials such as lavender. Just remember that nothing’s foolproof, and even if you do everything correctly, plants may not survive transplanting. That’s just nature!
One Final Word of Advice: Be Patient with Your Perennials
Some transplants, such as peonies, are a little fussy and don’t like being moved, so they may take a year or two after they’ve been divided before they bloom again, says Barshaw. No worries! Give all your perennials a granular extended release fertilizer in the spring, and then wait for nature to do its thing. Eventually, you’ll have lots of new plants!