Dividing Perennials

21 September 2005

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Do your perennials look like they could use a trim or maybe even more? Fall is a good time to take charge of some of these plants before they take charge of your garden and the process will revitalize them as well.

Most perennials left in the same place for more than 3 to 5 years are likely to be overgrown, overcrowded, have dead or unsightly centers, and need basic fertilizer and soil amendments. The center of the clump will grow poorly, if at all, and the flowers will be sparse. The clump will deplete the fertility of the soil as the plant crowds itself.

To divide mature clumps of perennials, select only vigorous side shoots from the outer part of the clump. Discard the center of the clump. Divide the plant into clumps of three to five shoots each. Be careful not to over-divide; too small a clump will not give much color the first year after replanting. Divide perennials when the plants are dormant, just before a new season of growth, or in the fall so they can become established before the ground freezes. Stagger plant divisions so the whole garden will not be redone at the same time; good rotation will yield a display of flowers each year. Do not put all the divisions back into the same space that contained the original plant. That would place too many plants in a given area. Give extra plants to friends, plant them elsewhere in the yard, or discard them. If you cut them into small pieces you might want to pot them up until they become established so you can take better care of them.

Divide perennials when plants are dormant before a new growth season. Be sure to retain sufficient rhizomes, tubers, or roots. These will supply the immediate nutritional needs of the divided plant until it can establish roots. Perennials such as Shasta daisies, hostas, chrysanthemums, hardy ferns, and some herbs are easily lifted and separated in the spring.

Dig and divide spring/summer-blooming plants in the early fall to enable their roots to become established before winter. If you cannot get to them before mid October, wait until next year.

Do not divide perennials with taproots such as butterfly weed and rue.

Division steps to follow are:

1. Prepare the site for your newly divided perennials by adding compost, peat moss, or aged manure, along with a light application of super phosphate or bone meal.
2. Lift the plants out of the ground, taking care not to damage the roots.
3. Gently shake off loose soil and remove dead leaves and stems.
4. Separate plants using your hands, a garden spade, fork, or knife (make sure your tools are sharp to minimize the wounds).
5. Discard the center of the clump if weak and woody or diseased and decayed.
6. Divide the vigorous plants into clumps of three to five shoots each.
7. Remove half the foliage from your new plants so water loss will be reduced.
8. Bearded irises should retain a few inches of rhizome and one fan of leaves, trimmed back halfway.
9. Replant the divided sections slightly higher than their original depth so they will be back to normal when the soil settles.
10. Replant as soon as possible so they do not dry out.
11. Label your new plants so you remember what you planted.
12. Water your new divisions thoroughly.
13. Apply winter mulch after the soil temperature drops following several killing frosts to prevent freezing.

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Contact your local Virginia Cooperative Extension office and speak with an Extension Agent or Master Gardener volunteer for more advice and information on lawn and landscape topics. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.