Dividing Perennials in Early Fall: Timing, Techniques, and Tools

As we turn to more casual tasks in the fall garden, less demanding than in peak summer, we can do the beneficial work of expanding our garden collection. Early fall is prime for dividing spring and summer-flowering perennials. The change of seasons offers mild conditions for young transplants to settle in before frozen soils and cold temperatures.

If you’re ready to do some garden rearranging, many of our favorite selections respond well to division and transplanting at this time of year. Dividing perennials in fall creates new plants and also rejuvenates the established crown. Division is an easy way to increase plant populations and to share the bounty.

Benefits of Division

Dividing perennials in fall brings a few key benefits. Division rejuvenates less vigorous or declining crowns. It reduces crowding, maximizing access to light, moisture, and nutrients to support growth.

Dividing frees up root and growing space and improves air circulation around stems. Less cramped conditions mean fewer pest and disease issues, and improved vigor boosts resistance. 

Division also manages size, controlling overgrowth and keeping robust spreaders in bounds. And, of course, division creates new plants to increase the collection.

While some perennials seldom, if ever, need dividing, others benefit every few years or even annually. It’s time to divide when established crops show fewer flowers, woody stems with less new growth, sparse foliage, and, especially, declining central crowns. It also helps to relocate and divide those in less-than-ideal conditions, like too much shade or soils that lack drainage, or if garden conditions have changed since planting.

Perennials to Divide in Fall

As our spring and summer-flowering perennials slow their growth toward season’s end, the transition marks a healthy time for division. When not in flower, they can direct energy into root production. If you noticed less robust blooms or crowded stems during the warm season, splitting them now lets them settle in before winter. 

From clumping, rhizomatous perennials to those with fleshy tubers, fall makes for a less busy season to divide. Spring is the best time for dividing fall perennials, and any we didn’t catch in fall.

Popular perennials to divide in fall include:

• Peonies
• Iris
• Phlox
• Daylilies
• Poppies
• Lilies
• Coreopsis
• Yarrow

Timing Fall Division

The best time for dividing perennials in fall is at least four to six weeks before the anticipated first frost, especially in cold climates. This advance lets roots develop, settle in, and absorb moisture before the soil freezes. Avoid digging, dividing, and replanting during extreme heat or frigid conditions, as they can stress young transplants.

September and October are often the best times to divide and transplant, including perennials like peonies. The tubers have adequate energy reserves from the growing season, and an early fall division gives tubers time to set new roots before heavy frost.

In addition to lessening stress, dividing in the fall gives a necessary chill blast over the winter for perennials that need it (like peonies).

Tools and Materials

Dividing perennials in fall is straightforward and only requires one or two basic garden tools. A digging fork, shovel, or spade lifts the clump. Clean, sharp pruners or a blade help cut the crown into sections and tidy the stems. 

Disinfect tools with an alcohol wipe, spray, or dip in 70% isopropyl alcohol, especially when pruning and clipping. Good tool sanitation helps reduce pest and disease spread. Sharp tools also minimize cuts that tear or shred stems or roots, creating wound entry points susceptible to disease.

Prep, Deadhead, and Cutback

Before dividing, we want to make it easy on the new plants to focus energy on producing strong roots for overwintering. Deadhead faded blooms, cut away weak stems, and remove any diseased portions (keep an eye out for powdery mildew with crowded stems).

Prepare the transplant area before dividing perennials in fall, whether in the existing growing spot or a different location. Remove any plant debris to prevent harboring and transferring fungal spores. Check soil quality and add compost to increase organic richness for those who prefer it. Lightly turn the soil to aerate it and promote root development for the transplants.

Water deeply the day before dividing for easy digging and turgid, water-filled stems and roots. Choose to divide on a mild, overcast day that’s not overly hot or sunny for the least stress on the new and existing plants.

How to Divide

How to divide specific perennials varies according to species, root size, depth, and sensitivities, but many rely on a similar technique.

With a spade or digging fork, dig a wide berth around the main crown or entire clump to lift it out of the soil. For some perennials, this may be only four to six inches away from the core, depending on the size and depth of the root system. Capture as many roots as possible, keeping the root ball intact. Loosen the roots and gently shake off excess soil.

With a sharp knife or spade, separate the clump or core into sections. Each segment should have three to five viable stems with roots attached (these become the new transplants). With clumping selections, it’s easiest to start from the outside of the clump, which holds the freshest shoots.

Gauge the viability of the mother plant to determine whether to replant it or not. If the crown is dense, woody, and showing less growth and flowering, compost the old portion and foster the new offspring.

Replanting

With new divisions ready, replant the segments as soon as possible for viability. Situate the plugs in their garden site according to proper spacing for the selection. Ample spacing allows for good airflow as shoots develop and room for mature growth.

Many species grow beautifully in containers. Plant the transplants in a high-quality potting mix. Ensure pots and potting media are well-draining. Prepare to overwinter them with protection in cold climates.

Location and Care

Water thoroughly after dividing perennials in fall to moisten the surrounding soil. Aim for even moisture, watering until the first frost. Regular moisture produces the hardiest specimens for overwintering.

Depending on your climate, seasonal fall moisture is often enough, supplemented with irrigation during dry spells. There’s no need for watering after frost or during dormancy when the transplants aren’t actively uptaking moisture.

In cold climates, add a thick mulch layer for fall-planted divisions as temperatures drop. Several inches of straw, pine needles, or leaf litter help protect against natural freeze/thaw cycles and frost heaving, which can damage the young, sensitive roots.