15 Perennials to Divide in Fall

Fall is a great time for many garden activities and could be considered one of the best times to divide perennials. The temperatures in fall drop and plants are finishing up their growing for the season. Dividing now allows them time to regenerate roots and get established before winter dormancy sets in.

Hosta (Hosta spp.) – In the fall divide hostas when the leaves are starting to turn yellow. I like transplanting hostas in the Spring right as the tips of the leaves are emerging from the soil. Hosta are tough plants and can transplant well nearly any time in the growing season but Spring and Fall are the best times.
Daylily (Hemerocallis) – Daylily clumps get crowded fast and can be divided into a number of divisions called fans. Shoot for divisions with at least 3 fans but if going for a lot of plants daylilies can be divided into single fans.
Iris (Bearded and Siberian) (Iris germanica, Iris sibirica) – Be sure to only replant fans with healthy rhizomes. Often borers can get into the iris roots and you don’t want them around. Pull or snap off those rhizomes and trim back the foliage. Look for foliage with brown leaf spots on them and remove and discard those.
Peony (Paeonia) – Peonies take a while to recover after a division so only divide if needed. The root systems are slow to re-establish.
Sedum (Stonecrop) (Hylotelephium spectabile, etc.) – Easy clump dividers. Sedum divides well at any time of the year. It can be propagated through division, leaf cuttings, or stem cuttings with a lot of success.
Black-eyed Susan (Rudbeckia fulgida and cultivars) – Rudbeckia is easy to divide and grows fast. The divisions can be made into small clumps and will quickly recover. It also self sows regularly so you may want to harvest the seed prior to digging around the plant to prevent too much reseeding in the same location.
Shasta Daisy (Leucanthemum × superbum) – Benefits from division every few years. These are beautiful flowers that can be propagated through cuttings as well.
Bee Balm (Monarda didyma) – Keeps mildew in check by renewing growth. Bee balm really takes well to division but if you have a taller variety you may have to cut it back to reduce the stress.
Phlox (Garden Phlox) (Phlox paniculata and P. subulata) – Dividing helps with air circulation. Ground cover phlox (moss phlox) takes very well to division. I
Coneflower (Echinacea purpurea) – Strong root clumps can be split and shared.
Yarrow (Achillea millefolium) – Vigorous spreader, rejuvenates with division.
Japanese Anemone (Anemone hupehensis) – Spreaders that can be thinned.
Astilbe (Astilbe spp.) – Clumps decline if not divided every few years.
Coreopsis (Tickseed) (Coreopsis verticillata, etc.) – Division restores vigor. You can also gather seeds in the fall for resowing in spring.
Ornamental Grass (like Miscanthus, Panicum, Pennisetum) – Divide mature clumps before they get woody. They can be divided in spring as well just after they are cut back when the new grass leaves are beginning to emerge.

How to Divide MOST Perennials

Most perennials follow the same tecnique when it comes to division. Some plants will vary a little, but here are the basics!

Dig up the clump – Use a spade or fork to lift the whole plant out, roots and all. Try to get under the crown so you don’t shear off too much root. I like to water the plant before actually digging up the clump or divide after a good rain. This loosens the soil and makes it easier to remove the clump from the ground.
Shake or wash off soil – Loosen the dirt so you can actually see the root structure. This makes it easier to spot natural divisions.
Separate the clump – Pull apart sections by hand if possible, or use a sharp knife, spade, or even two garden forks back-to-back for tougher crowns. Aim for divisions with 3–5 healthy shoots and a solid chunk of root. Soaking in water can help loosen the clump even further if you have trouble seperating the clump.
Trim if needed – Cut away dead or mushy roots. Some gardeners trim foliage back by half to reduce stress, especially on leafy plants.
Replant right away – Place divisions at the same depth they were growing before. You can pot them up in containers if you don’t have an immediate location for the plants. Water them in well to settle soil around roots and continue to water until established or dormancy.
Mulch and baby them a little – Add mulch to protect against frost heaving, and keep soil evenly moist while roots re-establish.

Some plants (like iris rhizomes or peonies) have quirks, but most clump-forming perennials follow this script. Irises you will want to remove any brown or spotted foliage and dispose of it. Iris rhyzomes like to rest of the soil surface some so don’t replant them too deep. If the rhizomes have any dead/rotted sections separate them off and dispose of them. Only replant the healthy looking rhizomes. Many people like to trim the foliage back but I tend to leave it if it still looks OK. My thought is that the foliage will help generate energy for the rhyzome to overwinter.

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