Also, when perennials are overgrown and crowded, they often won’t bloom as much, so dividing will help reinvigorate the flower show. However, not all types of perennials appreciate being divided. Here’s what you need to know for success.
When to Divide Your Perennials
While you can divide most perennials any time from spring to fall, those two seasons are best. Dividing can be stressful on the plants—and they’ll recover better from the shock in cool, moist conditions. That being said, if you want to divide your favorites in summer, wait until they’re large enough to be divided into several clumps, and keep them well watered once you’ve separated them.
How to Divide Perennials
Perennials such as asters, hostas, and yarrow can be divided easily with no hassle. You can also divide perennial herbs to expand your harvest. All you need to get the job done is a shovel and work gloves. Follow these simple steps to reach healthy-looking perennials.
Step 1: Dig the Clump
Dig up the clump of perennials that will be divided. To do this, insert the shovel deep into the soil around the perimeter to loosen the roots and isolate the clump. You can even use a garden fork or spade to help separate the roots. Test Garden Tip: Watering the perennial a couple of days before you dig it up will soften the soil and save you effort.
Step 2: Remove the Clump
Force your shovel or garden fork under the root ball and lever the ball up and down to loosen and position it on the shovel. Then, lift the shovel and root ball. Try to keep the root system as intact as you can. Once you dig the plant out of the ground, shake, wash, or brush any excess soil from around the root ball—this makes it easier to pull the clump apart.
Step 3: Separate the Crowns and Replant
Pry or cut apart individual crowns. Each clump needs to have leaves and roots in order to grow. Replant the separated clumps promptly so the roots don’t dry out. Plant them at the same depth as before and water well. Cover the soil with mulch to help conserve moisture while your newly divided plants become established.
Leave These Be
While most perennials benefit from being divided every few years, there are a few that thrive better if they’re kept intact. Avoid dividing these varieties:
Baptisia Bleeding heart (Dicentra) Butterfly weed (Asclepias) Christmas rose (Helleborus) Gas plant (Dictamnus) Lavender (Lavandula) Oriental poppy (Papaver orientale)
Divide Every 3 to 4 Years
Rule of thumb: Most perennials do best when divided every three to four years. When in doubt, this is the route you should take. These varieties include:
Astilbe Bee balm (Monarda) Black-eyed Susan (Rudbeckia) Daylily (Hemerocallis) Hosta Peony (Paeonia) Phlox Purple coneflower (Echinacea) Siberian iris (Iris sibirica)
Divide Every 2 to 3 Years
Some perennials need a little more attention. Divide these every other or every third year to keep them performing at their best.
Aster Blanket flower (Gaillardia) Clustered bellflowers (Campanula glomerata) Coreopsis Lamb’s ears (Stachys) Yarrow (Achillea)
