Dividing Perennial Plants

Dividing perennial plants is a quick way to multiply the plants in your garden and is also necessary every few years to maintain the vigor of some perennials.

Not all perennials need dividing, though. Peonies, for example can grow happily in the same spot for years and years and never need dividing, and if you do move them it will take them a couple of years before they are blooming happily again.

You can usually tell if a perennial needs dividing because it will not bloom as prolifically as in the past.  It may also develop a dead ring in the center of the plant. Siberian Iris is notorious for doing this. 

Late August or early September is a good time for dividing iris and lilies if you live in the Midwest, the South or Southwest.  They have finished blooming by then and dividing and replanting them now will give them time to establish new root systems before autumn so that they will be ready to bloom with new vigor next year. 

In general though, you divide spring blooming plants immediately after they bloom and ones that bloom later in the early spring soon after the crown starts to sprout, (which is why I'm writing this now as I have a few I want to divide and replant or give away).

Early spring when pips emerge is a good time to divide plants because of several reasons.  It's easy to see where everything is, the roots are small. There is a whole growing season ahead for plants to reestablish themselves and the ground is usually easy to work.

Actually, when you divide perennials varies a little depending on where you live, but anytime is OK as long as you do it about a month before very cold or hot weather sets in. Be sure to give your newly divided plants lots of TLC for awhile after transplanting them, though.

To divide tuberous plants like iris and lilies, dig up the whole clump and carefully pull apart several tubers.  One clump can be put back in your original hole and you probably have two or three more clumps that can be planted somewhere else or traded with a friend for something they are dividing.

Dividing perennial plants that have tough fibrous roots is usually done with shovel or sharp edged spade.  As before dig up the whole clump and then look for separate crowns within the clump.  With the end of your shovel sharply push downward and split the clump into pieces making sure to have a crown in each clump.

If the roots of the perennial you dividing are shallow you can sometimes divide your clumps with two garden forks to gently pull apart sections.

When you’re dividing perennial plants, it’s also a good time to enrich your soil and add fertilizer and mulch.  Even if you are using the same planting hole, you should loosen the soil all around the hole and carefully spread out the root ball as much as possible before replanting it.

It’s ideal if your newly divided plants are going immediately back in the ground, but this isn’t always possible so make sure to take some steps to protect your divisions until you can plant them. 

Sometimes I will temporarily plant mine in large containers and keep them well watered in a shady part of the yard.  Large plastic bags work well for sharing plants with friends. It is easy to slip the whole root ball into a big bag which I add water to and then tie the top of the bag around the stems.

If you keep the roots damp until you can plant them and then water well and regularly when you do, you should be very successful dividing perennial plants.  For added protection you might want to fertilize your new plant with a solution that encourages strong root growth.

It is perhaps intimidating to dig up a growing plant and chop it up into pieces, but once you do it and succeed, you’ll realize that perennials are pretty tough.  Your labor has just rewarded you with new plants and more flowers for the next growing season.

Happy gardening and thanks for gardening with Julie!