After a few years in your garden, clumps of perennial plants can grow too wide for their own good. Then they bear fewer flowers and, in some cases, die in the center. That means it's time to dig them up, slice them up, and either replant the smaller clumps — called divisions — or give them away.
Some plants are best divided in spring, some in fall, and some in either season:
- In spring, divide perennials that bloom in late summer or fall, such aster, joe-pye weed, chrysanthemum, obedient plant, ornamental grasses and hostas
- In either spring or fall, divide bee balm, black-eyed Susan and astilbe
- In fall, divide perennials that bloom in spring or early summer, such as peony, foxtail lily, Siberian iris and arum
How often to divide? Most perennials fall into one of these four categories:
Every 1–2 years: aster, chrysanthemum, obedient plant, spiderwort,blanket flower, coreopsis
Every 3–5 years if needed: fern-leaf bleeding heart, astilbe, bee balm, hosta ornamental grass, yarrow, tall phlox, tall bearded iris
Every 10 years if needed: lungwort, goatsbeard, lady's mantle, meadow sweet, meadow rue
Only when you want more of the plant: tall sedums, old-fashioned bleeding heart, gas plant, baby's breath, false indigo, most poppies, butterfly weed, candytuft, lavender, rosemary, and columbine
Time — 5–15 minutes per plant
Difficulty — Easy
Expertise — Know which perennials you grow and when they flower
Frequency — When needed, based on the plant's growth rate
Where — All US
Steps
- Use a spade to dig up the plant and as much of the perennial’s root ball as possible.
- Lift the whole plant from its hole, grab the clump by the leaves and shake it lightly to remove loose soil.
- Divide the clump into a few sections:
- If the plant is small, try ripping the root ball into smaller clumps with your hands, being sure each clump has roots, stems and leaves.
- If the root ball is too big to rip apart, set it on the ground and slice through the crown and root ball with a spade. It feels brutal and the plant gets a little beat up. Be brave.
- A few perennials have such tough root systems that they may require a saw, machete or hatchet to divide, such as bear’s breeches, goatsbeard, some ornamental grasses and ferns.
- Replant the divisions you're keeping. Put the ones you're giving away into a plastic bag or other container, water the roots lightly and place them out of direct sunlight.
Tips
- Consult a garden reference for perennials not listed.
- Dividing perennials on a cloudy, cool day minimizes their transplant shock.
