How many investments have you made that doubled in three to five years? Gardeners who plant perennials can watch their green assets multiply that fast–and all they have to do is figure out where to put the profits, also known as offshoots of the original perennial.
Given adequate light, moisture and fertilizer, most hardy garden perennials grow vigorously enough that one plant eventually needs to be divided into two or more clumps. Dividing a mature perennial is good for the plant, whose blooming energy may have been declining as the plant started to crowd itself. And it’s good for the gardener, whose time and energy spent in the garden are repaid in a steady crop of new plants at no cost.
“For a little bit of digging and chopping, what you get is a lot of new plants to fill in the garden or give to friends,” says Ruth Johnsen, who gardens in west suburban Batavia.
John Preece, a Southern Illinois University horticulture professor who specializes in plant propagation, points out that dividing a perennial gives the gardener a close-up view of the plant’s roots, the elemental support system for any plant but the part of it to which we pay the least attention. “It’s a great way to learn about plants and how they grow,” he says.
In this series of articles about the fundamentals of gardening, the primary focus has been on how to start a garden. That’s not where it ends, of course. Maintaining a garden over a number of years and extending the longevity of its plants is a skill not to be overlooked. Once the newness wears off, the garden is still out there asking to be watered and weeded. Dividing perennials, an easy chore, re-energizes both plants and planters.
Most perennials need to be divided every three to five years. There are two good indicators that a perennial is ready for division, according to Ann Marie VanDerZanden, an assistant professor of horticulture at Illinois State University in Normal:
– It blooms less abundantly than in previous years, and the decrease can’t be blamed on a drought or other environmental variables;
– Its crown looks dead or sickly in the middle but healthy around the edges.
Most perennials should be divided while still dormant and without leaves and flowers to support. That way the roots can go to work restoring themselves after division but before it’s time to feed a hungry above-ground biomass. Postpone division, Preece says, “and you decrease the plants’ ability to regain their strength.” The ideal time to divide perennials is in late March and early April. Nevertheless, Preece and VanDerZanden both acknowledge that most gardeners–especially novices–are more comfortable dividing plants when there’s some above-ground greenery visible. Seeing the spiky little sprouts atop the crown reassures some people; for others, the sprouts act as guides for where to divvy up the crown evenly. Both professors say that’s fine, but the less greenery the better.
To bolster your chances of multiplying your plant holdings successfully, divide perennials that bloom from late June through fall by mid-May at the latest, VanDerZanden says. “If you want to wait until there’s some growth visible above ground, OK,” she says, “but get in there before it looks like a full-fledged plant again.” Perennials that bloom in late spring and early summer should only be divided after they bloom, preferably in the fall when they’ve shut down their growth systems, she says.
Dividing is a simple process, but one that usually entails an acclimation period–for the gardener, not the plant. “The first time I divided my perennials, 15 years ago, I was afraid to disturb the little darlings,” Johnsen says, echoing the memories of many other gardeners. “I thought I’d better not hurt them, their little roots are so tender. But that’s not true. They don’t mind you digging them up and pulling them apart.” It is, after all, for their own good.
Johnsen advises steely action. “Just dig in there and be aggressive,” she says. VanDerZanden agrees, saying the risks are small. “The worst-case scenario is that what you divide doesn’t look good the first year. It’ll look fine when it grows in,” she says.
Begin by digging the crown and roots out of the ground. It’s better to err on the side of digging too deeply than to damage the roots needlessly, so dig in a circle at least 4 inches from the visible crown and angle the shovel toward the center only after digging at least 4 inches down. Excess dirt will fall away, while the roots will hold together.
To divide a perennial, use either a sharp-edged spade or a long-handled garden fork. You can pull some perennials apart with your fingers. Some perennials, those with deep root systems such as hosta, can be divided evenly in halves or thirds and all the pieces can be replanted. But those with shallow roots, such as catchfly, fare better if the divisions are taken from around the edges and the dying center is thrown away. (Many good reference books about perennials advise which method suits which varieties.)
Whichever method you’re after, the technique is the same: Just slice the crown apart. “Make sure each piece gets its share of the root mass,” VanDerZanden says. Some perennials come apart easily, as if they were attached by Velcro in the first place. Others demand aggressive cutting. “Have courage and do it,” Johnsen says.
How many divisions can you make from one plant? “It depends on how quickly you want the plants to get to their mature size,” Preece says, “but generally a plug that is an inch or two in diameter has a good chance of survival.”
Divisions ought to be replanted right away, but if kept moist and out of the sun, they’ll last up to a week out of the ground.
When preparing the site where you’ll plant your profits, fortify the roots by watering the holes with Vitamin B1, available at most garden stores, before putting the plants in. Position each plant so its crown is as high as the original was. In other words, don’t smother under an inch of dirt a top that used to be poking through the soil. Keep the soil moist for a week after planting.
And then sit back and watch your investment double itself again. If only stocks were so reliable.
