Divide (And Conquer) Weak Plants

By Susan Tito

The proverb “The cobbler’s children have no shoes” could have been written to describe my life. You see, I’ve come to the realization that I help others beautify their gardens, yet I often don’t take the time to tend to my own outdoor spaces.

That became glaringly apparent to me recently after inspecting my property and noticing that many of my perennials — those plants that live for more than two years — had tripled in size and are growing into each other. I also saw that other seemingly healthy, strapping specimens didn’t bloom much this year.

This could mean only one thing — it’s time to divide my plants!

Sandra Vultaggio, a horticulture consultant with Cornell Cooperative Extension in Riverhead, concurred with my assessment.

“The first indication of perennials in need of division is lack of vigor,” she said. “For example, if you have bearded iris that have stopped blooming, that’s a good indication that they need to be divided.”

Another sign it’s time to divide is when plants form a clump with a central dead zone, resembling a donut.

Although early spring is an ideal time to divide most perennials, some plants do well — and prefer — fall division.

“There’s a rule of thumb: Divide spring-blooming perennials in the fall and fall-blooming perennials in the spring,” Ms. Vultaggio said.

Fall divisions should occur between mid-September and mid-October (I give myself a cut-off date of October 15). The goal is to give your replanted divisions ample time to establish healthy roots before winter sets in.

The thought of dividing a plant can be off-putting to some gardeners, who fear that they will end up killing their plants. As long as you don’t divide when it’s too cold or hot outside, they will bounce back. Plants can be very forgiving!

To get started on division, you need to dig up your plant. Insert a sharp spade into the soil around the outer edge of the plant to loosen it, then remove it from the ground. To keep mess to a minimum, I move excavated plants to my lawn and perform the divisions there. An added benefit: Any soil particles that fall off the plant will enrich the grass.

There are different ways to perform divisions, and it comes down to the root of the matter — literally. Perennials have three kinds of root systems: fibrous, clumping and rhizomatous.

Plants such as coreopsis and coneflowers have fibrous roots, which are easily recognized by their spreading, dense masses. Depending on the plant, these roots can be separated either by using your fingers or cut apart with a sharp knife. My tool of choice is a hori-hori knife, which has a serrated blade and can slice through just about anything.

Large plants with extensive root systems can be divided by using two digging forks back to back and then drawing the handles away from each other. This enables you to pry apart smaller pieces in sections containing three to five shoots.

Perennials that are overdue for division can develop complex root systems that take on woody characteristics, which can be especially challenging. For these monsters, you may need to use an axe or handsaw.

To divide plants with clumping root systems, such as daylilies and hostas, take a sharp spade and slice through the center of the clump, creating two halves. Create additional plants by slicing sections off the smaller clumps.

For plants with rhizomatous systems, which have horizontal stems underground or just at the surface, use a sharp knife to remove sections that have been damaged by insects or disease, retaining a few inches of the rhizome and a fan of leaves that has been trimmed back. Replant rhizomes with the top showing just above soil level.

No matter the root system, divisions should be planted in the same site conditions and at the same depth as the parent perennial. The reward: Your plants will be reinvigorated, but there’s also another benefit.

“Dividing perennials increases the number of plants you have,” said Ms. Vultaggio. “You can place them in new locations throughout the garden or give them away as gifts.”

What happens if you don’t have room for all your new plants or nobody wants what you’re willing to share? Join the Freecycle Network (freecycle.org), a website where you can get or give away items — including plants. In no time at all, you’ll find new homes for all your plant babies.

Plant addition by division — that’s a win-win for everybody.

Susan Tito is a freelance writer and proprietor of Summerland Garden Design & Consulting. She earned a certificate in ornamental garden design from the New York Botanical Garden and is a member of the American Horticultural Society and Garden Writers Association. She can be reached at stito630@gmail.com.