15 Perennials to Divide in Fall

Perennials divided in the fall — Fall is the perfect time to divide many perennials. They'll be in the ground bright and early and ready to grow come spring.

Most perennials can be divided in either spring or fall; however, dividing your plants in fall can be particularly beneficial for perennials that flower in spring to summer. To limit plant stress, it’s best to divide perennials on days when the sky is overcast, and temperatures are cool. Replanting perennials as soon as you can is also recommended, and you can help your plants adjust more easily to your garden by watering them well after planting and then adding a thick layer of mulch to shelter their growing roots.

1. Daylilies (Hemerocallis spp.)

yellow daylilies in bloom — Dividing daylilies in fall gives them time to acclimate and regroup so they're ready for spring blooming.

Plant name:	Daylilies
Light requirements:	Full sun to part shade
Water requirements:	Moderate
Growing zone:	Zones 2 to 11

Daylilies are fast-growing perennials that form thick clumps of leaves as they spread. These plants should be divided every 3 to 5 years to keep them looking their best and to prevent their roots from becoming overgrown. If you forget to divide daylilies regularly, your plants can become overcrowded and stop producing blooms.

Daylilies can technically be divided in spring, but fall division is usually better as it will give your plants more time to acclimate before they need to bloom. To divide daylilies, dig up the plant’s root ball with a shovel and then insert two gardening forks, back to back, into the clump of roots. Pry the forks apart from each other to break daylily plants up into smaller sections before replanting your new plants into your garden bed.

2. Siberian iris (Iris sibirica)

Purple iris in bloom — Like many tubers, bulbs, and perennials, dividing irises increases their health and blooms.

Plant name:	Siberian iris
Light requirements:	Full sun to part shade
Water requirements:	Moderate
Growing zone:	Zones 2 to 9

Like daylilies, Siberian irises should be divided every 3 to 5 years, and they will start flowering less and less as the plant becomes overgrown. Siberian irises can also develop unsightly bald patches in the center of the plant when they need to be divided. This is always a clear sign that you need to break up your plants to give them more breathing room!

The division process of irises is very similar to daylilies, and gardening forks, shovels, or spades can be used to pry apart entangled roots. Make sure that each section of your new iris plant has a good clump of roots and a few leaves too. Cutting back the plant’s foliage before dividing irises and lilies in fall can make these plants much easier to manage, and it will also give you better access to the plant’s root system.

3. Peonies (Paeonia lactiflora)

Pink peonies that were divided in the fall — Peonies do better if divided in the fall. For most locations, September is the right time.

Plant name:	Peonies
Light requirements:	Full sun
Water requirements:	Moderate
Growing zone:	Zones 3 to 8

Peonies don’t need to be divided as often as daylilies and irises, but if your peony plants stop producing blooms, it may mean that it’s time to dig up your plants and split them. Make sure other factors aren’t at play, though, as peonies can stop flowering if they don’t receive enough light or if you plant them too deep. The best time to divide peonies is in September, as this will give your divided plants time to acclimate before winter sets in.

It's easiest to cut peony foliage down to the ground before dividing your plants. This has the added benefit of removing spent foliage that may contain powdery mildew spores and other plant pathogens that you don’t want overwintering in your garden. After digging up the peony roots, split the roots up into 6 to 8” sections, with each root section containing between 3 to 5 eyes.

4. Garden phlox (Phlox paniculata)

Pink flower tall phlox — Dividing phlox can help increase air flow around the plant, which helps it stave off mildew disease.

Plant name:	Garden phlox
Light requirements:	Full sun to part shade
Water requirements:	Moderate
Growing zone:	Zones 4 to 8

Like peonies, garden phlox can be prone to mildew issues, so if you divide your garden phlox in the fall, be sure to dispose of any diseased leaves in your burn pile or in the trash. Dividing garden phlox regularly will keep the plants looking trim, and it also supports flowering. Beyond that, dividing phlox plants will improve airflow and reduce the likelihood that mildew will develop.

Garden phlox plants grow quickly, and they should be divided every 3 to 4 years. Like many other perennials, garden phlox will stop flowering, and it may develop bald centers when it needs to be divided. When dividing phlox plants, make sure that each new plant section has between 3 and 5 healthy shoots and a nicely sized clump of roots too.

5. Bearded iris (Iris × germanica)

Bearded iris flowers — Bearded irises may need dividing as often as two to five years.

Plant name:	Bearded iris
Light requirements:	Full sun; part shade in hot climates
Water requirements:	Moderate
Growing zone:	Zones 3 to 9

Just as with Siberian irises, bearded irises need to be divided regularly for health and proper growth. Fast-growing plants may need to be divided every other year, while slower growers can be divided every 5 years. If you notice that your plants are blooming less, it’s a sure sign that it’s time to divide your plants.

While dividing bearded irises will help them bloom better, division can also reinvigorate the plant’s root system and reduce the incidence of soft rot and iris borers. Iris borers leave small holes in iris rhizomes, and they can cause streaking on the plant leaves too. If you notice these signs, be sure to snip off and dispose of the infected plant tissue to prevent the borers from reemerging in your garden next year!

6. Oriental poppies (Papaver orientale)

Orange oriental poppy in bloom — When you notice your oriental poppies aren't flowering much anymore, divide them.

Plant name:	Oriental poppies
Light requirements:	Full sun to part shade
Water requirements:	Moderate to low
Growing zone:	Zones 3 to 8

Oriental poppies are some of the most dramatic perennials you can grow in your garden, with paper-thin petals that come in shades of pink, red, and peach. But if your plants look a bit drab and they aren’t flowering as much, it may be time to divide them. Oriental poppies can be a bit of a challenge to divide because they have a long tap root; however, you can still divide these plants successfully with a bit of care.

The key to dividing oriental poppies is to dig in deep when you’re digging up the plant. Oriental poppy’s tap roots can stretch 12” long, so make sure you don’t damage the root too much when digging. Watering the soil line before you start can make the soil much easier to work with, and it will also help the plant’s roots release from the earth.

The best time to divide oriental poppies is from August to September when the plant is in a state of dormancy. Make sure that each section of your new plant division has several eyes each.

7. Lily of the valley (Convallaria majalis)

Blooming lily of the valley — Not only will regular dividing increase the bloom and health of Lily of the Valley, but it will give you more plants to love, too!

Plant name:	Lily of the valley
Light requirements:	Shade
Water requirements:	Moderate to low
Growing zone:	Zones 2 to 7

Lily of the valley is a fast-growing, mat-forming perennial that can thrive in shady gardens where it forms a low-maintenance, flowering groundcover. But this plant grows so thickly that it will need to be divided every 3 to 5 years. Dividing lilies of the valleys can give you additional plants for your garden, but if you end up with more plants than you can easily use, you can also give extra plants away to neighbors, family, and friends.

Lily of the valleys require more gentle handling when they’re being divided, but these plants tend to be easier to work with than daylilies and irises. To divide the lily of the valleys, dig up the plant’s rhizomes and then gently tease the plant sections apart to create new plant starts. Sow your new lily of the valley plants about 4” apart so they will have ample room to grow.

8. Hosta (Hosta spp.)

Variegated hosta plants — Hostas will reduce in size over four or five years if they are not divided regularly.

Plant name:	Hosta
Light requirements:	Part shade
Water requirements:	Moderate
Growing zone:	Zones 3 to 9

Hostas are another shade garden favorite, and these colorful foliage plants can make an impressive display when planted en masse under deciduous trees or in other low-light areas. However, hostas do grow quickly, and they will need to be divided every 4 to 5 years. If you don’t divide hostas regularly, your plants won’t grow as large, and they may produce fewer flowers.

Hostas can be divided in spring or fall, but September is usually the best time to divide these plants. To start off, water the soil well to make it easier to work with, and then dig up your clumps of hostas. Use a sharp gardening knife or spade to cut the hosta plants into sections with at least 2 to 3 eyes each, and try to avoid slicing through the roots if possible.

9. Black-eyed Susan (Rudbeckia hirta)

Black eyed Susan flowers — Black eyed Susans do best when divided about every four years. Air flow is important for these flowers.

Plant name:	Black-eyed Susan
Light requirements:	Full sun
Water requirements:	Moderate
Growing zone:	Zones 3 to 11

Black-eyed Susan is a beginner-friendly plant that can grow in a range of soil types, and it can even handle some drought. Famed for their golden yellow flowers, black-eyed Susans can bloom throughout summer and into fall, and then they produce large seedheads towards the end of the growing season. Allowing black-eyed Susan to self-sow is a great way to get new plants for your garden, but self-seeding can result in these plants becoming overcrowded.

To keep your black-eyed Susan growing strong and to prevent poor airflow around your plants, it’s recommended that you divide these plants every 3 to 4 years. Division should occur when the plant is in a state of dormancy – either in spring or fall. To divide these plants, simply dig up your black-eyed Susan patch and cut the plant sections into smaller clumps using a garden shovel, spade, or gardening forks.

10. Lady’s mantle (Alchemilla mollis)

Lady's mantle plant with water droplets covering it — Lady's mantle isn't a high maintenance plant, but it should be divided after several years.

Plant name:	Lady’s mantle
Light requirements:	Full sun to shade
Water requirements:	Moderate to low
Growing zone:	Zones 3 to 8

Lady’s mantle is commonly grown in cottage gardens, and it’s prized for its scalloped leaves and darling yellow flowers. A low-maintenance plant, lady’s mantle doesn’t require a lot of tending, but it does grow and spread over time. You can limit the spread of a lady’s mantle by deadheading spent flowers before they go to seed; however, even with deadheading, a lady’s mantle will need to be divided every few years.

How often your lady’s mantle will need to be divided will depend on the size of your plant, but it can be as often as every 3 to 10 years. Late summer to very early fall is the best time to divide the lady’s mantle, and you’ll want to avoid digging up this plant late in the season as it may make your plant less winter-hardy. To divide the lady’s mantle, simply cut the plant into smaller sections with your shovel or a spade, and be sure to replant the new plant starts immediately to keep them from drying out.

11. Astilbe (Astilbe chinensis)

Astilbe in bloom — Astilbe can easily become overgrown in just a few years' time.

Plant name:	Astilbe
Light requirements:	Full sun to part shade
Water requirements:	Moderate
Growing zone:	Zones 4 to 9

Astilbe grows quickly, and it can form a low-maintenance groundcover in shady and sunny areas. Famed for its foamy flowers that come in shades of pink, red, purple, and white, astilbe can become overgrown in a few years, which will limit the number and size of the plant’s flowers. But even if your astilbe isn’t overgrown, dividing your plants in early spring or late fall is an easy way to get more astilbe for your flower beds!

To divide astilbe, moisten the soil with your garden hose and then dig up clumps of the plant with your shovel. Use a garden knife or spade to cut the plant into smaller sections, taking the time to double-check that each new section of astilbe has plenty of roots and healthy shoots. Replant your astilbe as soon as you can and water your new plants in well to help them adapt to your garden beds before the cold temperatures arrive.

12. Oriental lily (Lilium auratum)

Double pink oriental lilies blooming — Oriental lilies can become patchy when older center bulbs die off. Dividing solves the problem.

Plant name:	Oriental lily
Light requirements:	Full sun to part shade
Water requirements:	High to moderate
Growing zone:	Zones 6 to 9

Oriental lilies and other lily species undergo a process known as naturalization as they mature. When this occurs, lily plants will spread and develop new bulbs, and the older bulbs at the center of the plant will die away with age. This causes lilies to spread, but it also results in lily plants developing bald patches at their centers.

To keep oriental lilies and other lily varieties from becoming patchy, plan on dividing lily bulbs every 2 to 3 years in the fall. September to October are usually good times to divide lilies, but you can also wait for the lily leaves to begin to droop and turn yellow at the end of the season. This signals that it’s time to dig up your lily bulbs and replant the younger bulbs in your flower beds, spacing them out so they have plenty of room to grow.

13. Salvia (Saliva spp.)

Purple flowering salvia — For the healthiest salvia plants, divide every two to four years.

Plant name:	Salvia
Light requirements:	Full sun to part shade, depending on a variety
Water requirements:	Moderate
Growing zone:	Zones 5 to 9

Salvia is one of the best plants to grow for pollinators, but it also adds a wealth of color to ornamental beds, cottage gardens, and other landscapes as well. Salvia plants don’t need a lot of upkeep, so they’re good choices for beginning gardeners. However, if you want to grow the healthiest salvia around, plan on dividing your plants every 2 to 4 years in spring or fall.

After gently lifting salvia roots from the soil, see if you can tease the roots apart to get new plant starts. If you can’t work the roots apart easily, cut the roots into smaller sections with a gardening knife or a hori hori. You can limit the amount of time your plants are out of the soil and help them recover more quickly after division by pre-digging your new planting holes before you dig up your salvia plants.

14. Japanese iris (Iris ensata)

Purple flowering Japanese iris in a pond — Dividing this plant helps keep it in the ground with access to water.

Plant name:	Japanese iris
Light requirements:	Full sun to part shade
Water requirements:	High
Growing zone:	Zones 4 to 9

Unlike most other iris types, Japanese iris crowns have a vertical growth habit, which causes the plant to slowly lift itself out of the soil as it spreads. This makes it hard for this water-loving plant to retain the moisture that it needs, and it can lead to Japanese irises drying out too quickly and becoming brown and wilted. To avoid this, Japanese iris plants should be divided at least every 3 to 4 years, but you may want to divide your plants even more often than that.

The division process for the Japanese iris is very similar to other irises -- the roots can be worked apart by hand, or they can be cut into sections with a sharp knife. Cutting back the plant’s foliage to a few inches above the soil line before you dig up the plant’s roots can make the division process much easier. It’s also wise to amend your soil with a bit of compost or aged manure before replanting Japanese irises, as the added nutrients will help your plant’s roots adjust to their new home.

15. Bugleweed (Ajuga reptans)

Purple flowering bugleweed — Dividing bugleweed helps control its spread and keep it from becoming overgrown.

Plant name:	Bugleweed
Light requirements:	Full sun to part shade
Water requirements:	High to moderate
Growing zone:	Zones 4 to 9

Bugleweed is a low-maintenance groundcover, and it can also be planted on sloping hillsides to control erosion. Beyond its colorful green, bronze, or purple leaves, bugleweed is beloved for its purple flowers, which are always a hit with bees. But while this undemanding plant doesn’t need a lot of extra care, it can rapidly spread, and dividing bugleweed regularly will prevent this plant from becoming overgrown.

Dividing bugleweed is as simple as digging up the mother plant and breaking it into smaller sections with your hands or a gardening knife. If any weeds have wound their way into your bugleweed patch, use this time to pick out the weedy growth and remove any brown or dead patches of bugleweed too. Then, replant your bugleweed starts in full sun to part shade and water your new plants in well to help them acclimate.

Frequently asked questions

Perennial plants being divided in the fall — A general rule of thumb is to divide perennials in fall four weeks before serious frost. This gives them time to acclimate and heel in for the winter.

How late in the fall can you divide perennials?

Different perennials may need to be divided earlier than others. Some perennials, like lady’s mantle, will grow best if you divide them in early fall, while other perennials can be divided in late autumn, as long as the soil is still workable. If in doubt, your best option is to research the particular type of perennial you’re working with to determine the best time for plant division.

Is October too late to split hostas?

In cool climates, September is the best time to divide hostas. However, if you live in a warmer location, you can divide hostas as late as October or even November. A good rule of thumb is to divide hostas at least 4 weeks before your first frost date.

What is a rule of thumb for dividing perennials?

As a general guideline, perennials that flower in spring and summer should be divided in fall, while perennials that flower in fall should be divided in spring. That said, sometimes you may need to work with the time you have, and if you know you won’t have time to divide your plants in spring, you may want to divide them in fall instead.

What are the benefits of dividing plants?

Dividing plants rejuvenates their growth and helps flowering perennials bloom more abundantly. On top of that, plant division can also be used to improve the appearance of fading perennials and boost airflow around your plants so they’re less susceptible to mildew and other fungal issues.

What happens if you don't divide plants?

Perennials that aren’t divided regularly can become overgrown and overcrowded. This can reduce the health of plants and leave them more susceptible to mildew and pests. What’s more, plants that aren’t divided will often not flower as much, and they may develop unsightly barren patches in their centers, which can affect the look and feel of your flower garden.

Which perennials should not be divided?

Many perennials will benefit from plant division, but there are some exceptions. Some of the perennials that should not be divided include baby’s breath, false indigo, gas plant, and columbines.

Summary

A gardener dividing perennials in the fall — Dividing plants isn't hard and it will have a big impact in the looks and health of your perennial garden. And you get more plants!

If you’ve never divided plants before, you may be reluctant to pick up your gardening spade and dig up perennials that appear to be thriving. However, dividing plants is an easy way to improve their growth, and your plants will be much healthier if you stay on top of plant division. Waiting until your plants are overgrown can make dividing perennials much harder, and it also makes plants more susceptible to pathogens.

I find using a gardening journal or online calendar useful for keeping track of when I need to split perennials. To discover more helpful fall maintenance gardening tips, check out our guide on the perennials that should be pruned in autumn.

Comments

Jackie

August 25, 2023 at 10:39 pm

#6 Oriental Poppies BUT also under "Which perennials should not be divided?" So, which is it: Divide or not divide?

- Mary Ward
  
  August 30, 2023 at 7:54 pm
  
  Apologies for the confusion. Some poppies don't like dividing but oriental poppies should be divided in the fall--BUT they need to be divided early in the fall. This may have been part of the confusion. We've made corrections. Thank you for bringing it to our attention.
  
Deb Ross

August 27, 2023 at 11:21 am

In the list, oriental poppies is included. But in the commentary following, oriental poppies are listed as plants that should NOT be divided. So, which is correct?

- Mary Ward
  
  August 30, 2023 at 7:54 pm
  
  Apologies for the confusion. Some poppies don't like dividing but oriental poppies should be divided in the fall--BUT they need to be divided early in the fall. This may have been part of the confusion. We've made corrections. Thank you for bringing it to our attention.