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When To Divide Your Perennials & 6 Things To Help You Decide

When To Divide Your Perennials & 6 Things To Help You Decide

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Dividing might not seem like much, but it has so many benefits for your perennials. It can double their growth or double your stock, and leave you with flourishing plants year after year.

However, one trouble gardeners have with this task is that they don’t know exactly when to do it. And there’s no simple answer.

It depends on your plants and the climate you live in, so you have to approach each plant individually.

But, I have some tips that can help you decide the right time to divide your perennials properly.

Let’s get started!

Perks Of Dividing Perennials

One of the reasons why your flower stems have gone crooked may be overcrowding. It can also cause the center of your plant to start dying. Densely populated plants may also start producing less and less flowers.

Dividing your perennials will prevent overcrowding in your perennial beds and improve your plants’ growth.

Once you divide your plants, the roots will get more room to expand and the plant won’t have to waste its energy on dying foliage and stems. Instead, it will focus on producing as many flowers as possible.

Another perk of dividing your plants is to control their growth, so exactly the opposite of the first one. Certain perennials grow vigorously and can overtake your garden in an instant, choking out your other plants.

To prevent this from happening, simply divide them to keep them in check. You can plant them in other parts of your garden or give them to your family, friends, or neighbors.

Finally, dividing plants means you’ll have more of them, which is always a nice bonus. You can even plant them in containers, which will control their growth and still give you a nice display.

6 Things That Determine When To Divide Perennials

We can’t divide all plants at the same time. Plants themselves (and the conditions in which they grow) give you cues for when to do this chore.

Here’s what to look out for!

1. Plant Age

Perennial plants grow optimally when you divide them every 2-4 years. However, it really depends on how fast your plant grows.

For instance, if you have slow growers, you might not need to divide them more frequently than every 5 years, while some extremely fast-growing perennials benefit from a 2-year division.

Of course, you can divide your plants sooner than this if you want, but there’s generally no need.

Additionally, you should divide plants with deep roots when they’re younger, every 1-2 years. They generally don’t like to be divided and will suffer even more if you wait until they develop massive root systems.

It’s crucial to know the growth habits of your plants and their requirements, but here is a table that can help you decide when to divide certain perennials.

2. Flowering Season

A general rule of thumb is to divide spring-blooming perennials in fall and fall-flowering perennials in spring.

But you don’t have to blindly follow this rule because each plant has its preference. And yet, this technique takes advantage of the time when your plant is not flowering. 

Dividing them at this time will allow your perennials to divert their energy into forming a strong and healthy root system instead of dividing it between growing roots and producing flowers.

On the other hand, not many plants prefer summer and winter division. That’s because temperatures in the summertime are too high and can stress out your plants, or your perennials may be in the midst of their flowering season.

In winter, temperatures are way too low for your plants to establish roots, which can stop them from growing or even kill them in some cases.

Technically, you could divide your plants in late summer or late winter, depending on the climate and temperatures you have during these seasons. But your best bet is to keep with the spring and fall division.

3. Size

You can always divide your plants sooner than their age or flowering season dictate if you want to move them to a different location or you simply want to have more of them.

However, you need to make sure that they are large enough and, more importantly, have enough roots to withstand the division.

Mature and established plants don’t have these issues, but you have to be very careful about the amount of roots your younger perennials have.

4. Plant Health

You can improve the health of your perennials by and large by simply dividing them every couple of years.

However, this process can be very stressful, so you need to make sure your plants can handle it. If your plants are over or underwatered, are dealing with pests, or are infected with some disease, you should first treat this issue and then divide them.

Division will only stress out your plant even more, causing its health to deteriorate. That’s why it’s always best to stabilize your perennials first before putting them through more stress.

But if your plants have root rot or some other issue concerning the roots, or are planted in a location where they don’t get an adequate amount of light, you should uproot them. You can then deal with the issue, divide them, and transplant them to a more favorable location.

5. Climate

Your climate and USDA hardiness zone play a huge role in dividing perennials, especially in fall.

When separating your plants’ roots in fall, you need to ensure they have enough time to develop their new root system before frost hits. If you divide them too late, cold can kill new and fine roots, resulting in a stressed, stunted, or even dead plant.

The exact division time will depend on the growth rate of your plant. Generally speaking, you should divide your plants approximately 4-8 weeks before first fall frost, with slow growers needing early division in order to establish.

And if you live in northern parts of the US (or hemisphere in general), it might be best to wait for spring to divide your perennials. That way, your plants will have more than enough time to establish a strong root system before winter.

There’s less risk of frost hindering your division, and you can always sacrifice a couple of flowers this year to have healthy growth the next couple of years.

6. Temperature

Temperature is the only factor that affects day-to-day division times. For instance, the best time for dividing daylilies is during cooler temperatures and the same goes for other plants. That’s why we typically divide them in spring or fall.

You should also separate the roots of your perennials in early mornings and overcast days. Division in hot weather will cause more stress to your plant by causing it to dry out faster.

That’s why you should irrigate your plants prior to division to mitigate the effects of transplant shock.

How To Divide Perennials

One of the most common fall gardening mistakes is not dividing your perennials properly. Here are some steps that can help you out:

Step 1. Water your plants thoroughly before dividing them to make the soil easier to work with. Or do it after it rains.

Step 2. Dig into the soil a few inches away from the outer parts of your plant and its root zone. This will prevent accidental tearing of your plant’s roots.

Step 3. Uproot the entire plant using a spade or a shovel. Plants with deeper root systems will be much more difficult to lift, which is why you should divide them more frequently.

Step 4. Remove the excess soil around the roots to expose them and help you decide where to divide your plants. Let the naturally occuring clumps of stems be your guide.

Step 5. Separate the roots with your hand and cut them with a sharp and clean knife. If you have a small plant, only divide it in two. And if you have a large perennial, you can separate it into several individual plants.

Step 6. Transplant the divided plants immediately into soil and water them well to help the roots adjust to their new home.

Final Thoughts

Don’t forget to divide your perennials every couple of years to keep them refreshed and rejuvenated. They’ll reward this hard work with gorgeous flushes of flowers afterwards.