Multiplication by Division
Daylilies, a fail-safe perennial. The Daylily Collection at Berkshire Botanical Garden represents years of hybridizing and dividing.
By Thomas Christopher
Relax: what follows is not some remedial course in basic mathematics. In fact, what I am about to encourage you to do seems to violate that discipline’s basic rules. For by dividing your perennials, you can increase their sum. And in the case of several perennial stalwarts, this is the season to undertake that operation.
How many gardeners could get along without daylilies, bearded irises, and herbaceous peonies? They are the most reliable of perennials, hanging in with little or no care for decades. Indeed, I’ve found these flowers continuing to bloom in abandonment alone in some woodland opening or meadow long after the surrounding garden, and even the accompanying house, has disappeared. But they will bloom far better with a little bit of timely care.
These perennials will tell you when they need to be divided: the clumps will sport lots of leaves but fewer flowers, and may even thin as they die out at the center. All these symptoms indicate that the roots need more room.
Daylilies, the closest thing there is to fail-safe perennials, are also the easiest of this trio to divide. Just stick a garden fork into the ground about 6-12 inches beyond the outer edge of the daylily clump and use the fork’s handle as a lever to pry the clump loose (gently) from the soil. Repeat this operation in a circle all around the clump and the crowded daylily plant should pop out, roots and all. Then take a pair of garden forks and insert them, back to back, in the center of the exposed clump and pull on the handles to tear the clump of stems and roots into two pieces. If the two newly separated pieces are large, this process can be repeated to turn the two “divisions” into four. Finally, replant the divisions, excavating wide, shallow holes half a foot wider than the respective divisions and just slightly deeper. Set each division in the center of a hole and fan its roots outward before replacing the excavated soil and gently firming it back into place. Water well and tuck in with an inch of some organic mulch.
The same basic procedure can be applied to all sorts of rhizomatous irises (the kinds that spring from fleshy, subterranean stems). Instead of using back-to-back forks, however, you’ll use a knife to divide the irises’ clumps of rhizomes. Slice the clump into pieces, dipping the knife blade into a solution of household bleach and water (one part bleach to ten parts water) after each cut. Discard any parts that are soft and slimy – such parts are suffering from a disease called “soft rot” – and any rhizomes that exhibit signs of tunneling by iris borers. Cut the remainder into lengths of rhizomes up to six inches long, each one with an attached fan of leaves. Shorten the leaves by 2/3rds, then replant each piece in its own broad, shallow hole, setting the rhizomes so that their tops are at ground level. Replace the excavated soil, leaving the tops of the iris rhizomes just barely exposed, firm the soil, and water.
Peonies also have their own peculiarities. Unearth the clump, cut back the foliage to the ground and wash the soil from the roots. Here and there, sprouting from the roots, will be little pink, dormant buds, that are known as “eyes.” With a sharp knife, slice the clump into pieces so that each one has 3 to 5 eyes. Replant in the usual broad, shallow holes, taking care to set the clumps so that the replanted divisions will rest with the eyes an inch or two below the surface of the soil – set them deeper and the resulting plants will produce leaves but no flowers. Be sure to give your peony divisions plenty of room, setting them a couple of feet apart, as peony plants will grow quite large.
All these plants prefer a site with at least a half day of full sun, and full sun is better. Set them in the shade and they may survive, but they won’t flower satisfactorily. Plants don’t reward wishful thinking.
Be-a-Better-Gardener is a community service of Berkshire Botanical Garden, one of the nation’s oldest botanical gardens in Stockbridge, MA. Its mission to provide knowledge of gardening and the environment through 25 display gardens and a diverse range of classes informs and inspires thousands of students and visitors on horticultural topics every year. Thomas Christopher is the co-author of Garden Revolution (Timber press, 2016) and is a volunteer at Berkshire Botanical Garden.berkshirebotanical.org.
Caption: Crocus speciosus ‘Conqueror’ — a perfect choice in fall blooming bulbs that naturalize and spread.
Thomas Christopher is the co-author of “Garden Revolution” (Timber Press, 2016) and is a volunteer at Berkshire Botanical Garden. berkshirebotanical.org
Be-a-Better-Gardener is a community service of Berkshire Botanical Garden, one of the nation’s oldest botanical gardens in Stockbridge, MA. Its mission to provide knowledge of gardening and the environment through 25 display gardens and a diverse range of classes informs and inspires thousands of students and visitors on horticultural topics every year. Thomas Christopher is the co-author of Garden Revolution (Timber press, 2016) and is a volunteer at Berkshire Botanical Garden. berkshirebotanical.org.