In autumn, there are typically fewer tasks to do in the garden, but fall is the perfect time to divide many perennial plants since temperatures are cooler and plants aren’t growing as vigorously at this time of the year. Plant division helps to rejuvenate plant growth, and it keeps plants healthy too. But if you’ve never divided perennials before, you may not know where to start.
To help you out, we’ve compiled this beginner-friendly guide to teach you all the tips and tricks you need to know to divide perennials in autumn. Below, you’ll also find some suggestions that will help your plants readjust to your garden beds quickly, well before winter arrives!
- Why divide perennials?
- How to know if perennials need to be divided
- When to divide perennials in fall
- How to divide perennial plants in 8 easy steps
- 1. Time your plant division correctly.
- 2. Water the soil first.
- 3. Start digging.
- 4. Divide plant roots and stems.
- 5. Clean up your plants.
- 6. Replant your perennials.
- 7. Water them in.
- 8. Add mulch.
- What perennials can be divided in fall?
- Frequently asked questions
Why divide perennials?
Some perennials, like lavender and foxglove, should never be divided, and these plants can only be propagated from stem cuttings or seeds. However, many common perennial plants, including irises and daylilies, need to be divided every few years to keep them growing strong. While there are many reasons why you may want to divide the perennials in your garden, some of the key perks of dividing perennials include:
- Better growth.
Most perennials should be divided about once every 3 to 5 years. Dividing plants regularly gives perennials room to grow, and it keeps plant roots from getting overcrowded. In turn, this helps perennials produce more leaves and grow more prolifically!
- More flowers.
Regularly dividing perennial plants doesn’t just help plants produce more leaves… it also encourages plants to bloom more abundantly. Overgrown plants may not flower as much, but this can often be remedied with plant division.
- Prevents overgrown plants.
Pruning plants from time to time keeps plants from getting too large, and it also makes it less likely that fast-growing perennials will smother out neighboring plants. While following plant spacing recommendations is always advised, plant division can also make large perennial plants more manageable.
- Reduces plant diseases.
As plants become overgrown, their thick, leafy growth reduces air circulation, and this increases the chances that powdery mildew and other fungal diseases will arise. Dividing plants every few years is an easy way to improve airflow and prevent plant diseases at the same time!
- Tidier-looking garden beds.
If you prefer a more manicured garden aesthetic, dividing your plants every few years will keep plants much smaller and more manageable. Dividing perennials also gives you the opportunity to rearrange your planting designs and relocate plants that aren’t thriving to new sections of your garden where they may grow better.
- Fewer weeds.
Since you need to dig up perennials during plant division, you can use this opportunity to pluck out weedy growth. This will keep garden beds looking trim, and it will prevent weeds from getting a foothold in your garden too.
- More plants.
Of course, one of the main benefits of dividing perennials every few years is that it’s a great way to get more free plants for your garden. Every time you divide perennials, you’ll end up with one or more new plants, which can either be planted in your garden or given to friends and neighbors. If you end up with more perennial plants than you know what to do with, you can also host your own community plant swap!
How to know if perennials need to be divided
Not all perennial plants need to be divided, so it’s a good idea to do a bit of research on the types of plants you’re growing to determine if your plants need to be divided or not. However, sometimes perennials will actually let you know that it’s time to divide them, and if they do, you’ll need to pull out your shovel and get to work! Some key signs that will let you know that it’s time to divide your perennial plants include:
- Fewer flowers.
If your perennials have been growing in the same spot for years, but they’ve recently been producing fewer and fewer flowers, there’s a good chance that your plants may need to be divided. Of course, plants can stop flowering for other reasons, too, so this reduced flowering doesn’t always mean that you need to divide your plants. Low light, pests, and plant pathogens can also cause plants to produce fewer flowers, and some plants, like peonies, may not flower if you plant them too deep.
- Reduced growth.
Perennials that need to be divided won’t flower as much, but they may also stop producing as many leaves, and growth may become stunted as well. Again, low light, limited watering, and other factors can also slow plant growth; however, if your perennials haven’t been divided in a few years and they have stopped growing as much, it may be time to divide them.
- Overgrown plants.
Sometimes it's obvious that plants need to be divided, such as when perennials have gotten too large for the beds they’re growing in. Overgrown perennial plants can look messy, but they can also crowd out their neighbors and invade sections of your garden where you don’t necessarily want perennials to grow. If this occurs, there’s a good chance that you need to divide your plants!
- Leggy stems.
While some plants may stop growing when they need to be divided, other plants may display poor growth and stretch and produce leggy stems. This can also occur if your plants aren’t receiving enough light, but if your plants are receiving plenty of sun and they still look leggy, plant division may help.
- Bald centers.
One of the most obvious signs that perennial plants need to be divided is that plants will develop bald patches at the center of their growth. This is particularly common with irises, but other popular perennial plants can develop this symptom when they need to be divided as well. Bald centers typically emerge because plants produce new roots and leaves on the exterior of the plant, while the oldest section at the plant’s center dies away from age.
- Weedy beds.
Weeds aren’t exactly a sign that perennials need to be divided; however, if your perennial beds are getting overgrown with weeds, dividing your plants may help. When you dig up and divide perennial plants, you can take advantage of the opportunity and also pick out and destroy any weeds that have woven their way in between your perennials’ roots and leaves.
When to divide perennials in fall
Before you start dividing any plants in your garden, make sure you research the particular plants you’re growing for any plant division tips. While some perennials should never be divided, plants that do benefit from division don’t all need to be divided at the same time. For example, plants that bloom in autumn and plants with woody stems are typically divided in spring, while plants that bloom in spring and summer are often divided in fall.
The best time to divide perennials is typically on cool, overcast days and after recent rain. Dividing plants in the early morning or in the evening is also recommended, as plants are less likely to be stressed. Dividing plants under hot, bright sun is not recommended.
For best results, aim to divide your plants at least 4 weeks before your first frost date. Dividing your plants too late in the season may make your plants more vulnerable to winter damage, and plants may not have enough time to develop a solid root system before the ground freezes. Some plants may need even more time to adjust before frost arrives, so do your research and make sure your plants have plenty of time to acclimate before winter starts.
How to divide perennial plants in 8 easy steps
Dividing perennial plants can feel a bit intimidating at first, but it’s easier than you may think. All you need are a few simple tools, like a shovel or spade, and a pair of gardening forks. It’s always best to replant divided perennials immediately, but if you don’t think you’ll get around to replanting perennials on the same day, you may also want to have a tarp and some plastic plant pots to store your plants in until you have time to plant them.
1. Time your plant division correctly.
Ideally, perennials should be divided at least 4 weeks before your first frost date, and it’s best to divide plants immediately after a rain. If it hasn’t rained in a while, you can still divide your plants, but do it on a day when the weather is cool, and the sky is overcast. Whenever possible, avoid dividing perennials during hot weather and full sun, as plants are much more likely to suffer from stress and transplanting shock if they’re divided under these conditions.
2. Water the soil first.
If it has recently rained, you can typically skip this step. However, if it hasn’t rained for a few days, water your perennials and the soil around them well the day before you intend to divide your plants. This will irrigate your plants and help to loosen up your soil, and more importantly, well-watered plants are less likely to suffer from transplanting shock!
3. Start digging.
After watering your plants well, it’s time to get to work. Start digging up your perennial plants with your shovel or spade, but take care as you work around the plants’ root systems and try not to damage the roots if possible. You’ll be less likely to cut through plant roots if you start digging at least a foot or two away from the base of your plants.
Once you’ve dug all the way around the base of your perennials, gently lift your plants out of the soil and shake away any loose dirt clinging to their roots. It’s best to replant perennials immediately after plant division, as this will reduce the chances of transplant shock.
However, if you know you’re not going to have time to replant perennials right away, you can pot your perennials up in plastic pots and store them on a tarp in a shady section of your yard until you’re ready to divide and replant them. Just be sure to keep your plants well-watered in the meantime so they don’t dry up!
Tip: While it’s not necessary, you may want to clip back the long leaves of plants like daylilies or irises before you start dividing them. Cutting plant foliage back by half will make some plants simpler to work with, and it can also make it much easier to access plant roots when digging. What’s more, cutting back plant foliage can help plants adapt to new planting holes quicker since they can redirect their energy towards root growth.
4. Divide plant roots and stems.
Now that your plants are out of the soil, you’re ready to start dividing your perennials. But there are a few ways to go about it.
If your plants are small and have a relatively loose root system, you can often tease perennial plants apart with your fingers. On the other hand, larger perennials with interwoven root systems will often need to be cut apart with a gardening knife, shovel, spade, or a pair of gardening forks.
Personally, I find gardening forks to be particularly useful for plant division, especially when I’m working with plants like irises and daylilies. All you need to do is insert two gardening forks, back to back, into the center of your perennial plants and then pry the plants apart to separate their roots. If needed, this process can be repeated to separate clumps of perennials into smaller and smaller sections.
Depending on your plants and your transplanting goals, you can break perennials up into very small sections, or you can leave plants in larger chunks. Just make sure that each new plant division has a healthy clump of roots, and at least three plant stems or shoots.
5. Clean up your plants.
Next, inspect each new perennial division and clip away any diseased or broken stems and leaves and any mushy plant roots. If you see any signs of plant diseases or pests, cut those away too and pick out any weeds that may have woven in between your plant roots and stems. If you haven’t already clipped back the leaves of plants like daylilies and irises, you can also snip back the long leaves of these plants at this time.
6. Replant your perennials.
With your new perennial plants, all cleaned up and ready to go, you have a few options. You can either replant your perennials in your garden, or you can pot them up in plastic pots and bring them to a plant swap, or gift them to friends.
If you’ve decided you’d like to keep your perennials, locate a good spot in your garden where your plants will receive the light, nutrients, and moisture they need. Then, dig a hole that is as deep as your plant’s root ball and about 2 to 3 times as wide, and mix some compost (if needed) into the soil. After that, locate your new perennial plant in the planting hole so it is at the proper depth, backfill the hole with soil, and firm up the earth around your plant’s stem.
As with any plant, be sure to follow proper spacing recommendations when replanting perennials so you don’t accidentally sow your plants too thickly.
7. Water them in.
Once your plants are back in your garden, water them with a good, deep drink of water. Generally speaking, there’s no need to fertilize perennials after replanting them in fall as plants enter a state of dormancy in autumn, and they have no need for extra nutrients at this time. Compost, however, can still be useful to perennials during autumn as compost breaks down slowly, and it serves as a slow-release fertilizer over the course of the winter and early spring.
Plants may droop a bit after they’ve been divided and transplanted, but this is usually no cause for alarm. Most of the time, perennials will perk right up after watering or after they’ve had a bit of time to readjust to their new growing location.
8. Add mulch.
Mulch isn’t strictly necessary, but it can be beneficial to most perennials – especially when they’ve recently been divided and transplanted. Organic and natural mulches, like wood mulch and pine needles, add extra insulation around plant roots and serve as a buffer against winter’s chill. On top of that, mulches help lock in soil moisture levels, which keeps plants from drying out as quickly and reduces the amount of water your plants need.
If you do decide to mulch your perennials after planting, spread a 1 to 3” layer of mulch around the base of your plants, but make sure the mulch isn’t touching your plant stems. Mulch applied too close to plant stems can encourage rot and other issues.
What perennials can be divided in fall?
Many perennials that bloom in spring and summer should be divided in autumn, about once every 3 to 5 years. We have a full guide on the best plants to divide in fall, which you may find useful. However, to get you started, some of the most common plants that are divided in fall include:
- Bearded irises
- Garden phlox
- Oriental lilies
- Lily of the valley
- Lady’s mantle
- Black-eyed Susan
- Siberian irises
- Japanese irises
Frequently asked questions
That depends. In general, perennials that flower in autumn should be divided in spring, while perennials that flower in spring should be divided in autumn. That said, some perennials don’t need to be divided at all, so it’s best to research the specific plants you have in your garden before you start dividing them.
One of the most important things to remember about dividing perennials is that most perennials will grow best if they’re divided about once every 3 years. Fast-growing plants may need to be divided more often than that, while slow growers may only need to be divided once every 5+ years.
A shovel is an essential tool if you want to divide perennials, but a pair of gardening forks can be useful as well. When inserted into a tough clump of perennial roots, gardening forks can be used to pry plant roots apart, and they generally do less damage to plant roots than shovels and spades.
Typically, hostas are divided in fall, about 4 weeks before frost is expected. In cool climates, hostas are usually divided in September, but they can be divided even later in warmer regions.
It can be! While many gardeners cut plants like daylilies and irises back immediately after they finish flowering, this can actually harm plants and reduce the amount of flowers they produce next year. Waiting until after the first frost of fall to cut perennials back gives plants more time to grow and store the energy they need to survive the winter.
That depends. Spring blooming flowers are typically transplanted in fall, while fall blooming flowers are transplanted in spring.
Along with watering, fertilizing, and mulching, plant division is another important part of perennial plant maintenance, but it isn’t that complicated. As long as you divide your plants at the right time of the year and make sure your new plants have plenty of healthy roots to sustain, then dividing perennials is very similar to planting new nursery plants in your garden. But with an added benefit: divided perennials from your garden are free!
Once your new perennials have been planted, don’t forget to add some mulch and compost too. If you’re new to working with either product, you can find a list of our favorite mulches here and a guide on making homemade compost here. Happy planting!