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Should Perennials Be Divided in Fall or Spring?

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Do you know when to divide perennials?

Dividing perennials can help your garden in many ways. This practice can help you save money. And it may keep your garden blooming better over time. And those things make for a great garden! However, if you don’t know the optimal time to divide your perennials, you might make a big mess of things. And when that happens, your garden might look not so great for a while.

When to divide winter blooming perennials isn't when they're blooming

Using your own garden as a nursery is a great way to save money!

Often it pays off to purchase fewer or smaller perennials. That’s because many perennials grow and spread rapidly. And when many perennials become overgrown, your garden is now like a nursery. That’s because you can divide those perennials. And by dividing them, you can replant the parts of the plants you dug up. So this allows you to fill in new areas of your garden without purchasing more plants.

This practice can help save money. And by planting more of the same plants throughout your garden, you can create design repetition, which means creating consistent looks and themes and colors and forms in your garden. And in the end, this repetition can create calming, finished looking gardens.

Moreover, some perennials stop blooming well if they aren’t divided. Good examples of this are iris and daylily.

When is the best time to divide your perennials?

Are you wondering if spring or fall is the best time to divide your perennials? If so, you’re not alone in asking that question. And there there isn’t a one size fits all answer. However, the basic answer is to divide perennials when you have the time. But to divide successfully and without making a mess may mean more than just digging in any old time.

When is the worst time to split your plants?

Ideally, avoid dividing perennials that are blooming or as they are just getting ready to bloom. One reason for this is that key nutrients a plant uses to build strong roots are the same as those required for flowering and fruiting. So if I do decide to divide the plant while it is blooming, I may also cut all the flowers off to help the plant root in well. That’s because if it tries to do both root and flower simultaneously, it may give up the ghost.

Is fall the best time to divide perennials?

Fall is a great time to divide most perennials. And there are a few reasons dividing perennials in fall is often the best time:

  • It’s easy to do divisions during fall clean up
  • The main growing season has just ended, so knowing which garden beds need filling in may be fresh on your mind
  • Overgrown perennials that didn’t perform well in the just-finished season are obvious
  • Perennial top growth is usually still in view, so you can easily find the plants to divide
  • Plants divided and transplanted in fall benefit from being in place to settle in underground ahead of spring re-growth
  • Splitting plants isn’t as likely to be as hard on many plants as it might be in spring
  • Fall is when the garden is going dormant, so digging and splitting usually isn’t as visually disturbing as it may be in spring

A few perennials to divide in autumn:

Is spring a good time to divide perennials?

Sometimes spring is a great time to divide perennials. This is especially true for plants that may bloom well into fall. That’s because disrupting plants at their peak just makes our gardens look worse. And dividing when plants are blooming can also be hard on the plants. However, when dividing in spring, it’s generally best to complete divisions as early as possible. That’s because once the plants begin growing rapidly as spring progresses, its easy to make a mess of things digging and chopping their tender new growth.

Another note on spring divisions…sometimes spring soils are more conducive to digging than dry fall soils. This is especially true if the summer prior to fall was terribly dry.

A few plants that may benefit from being divided in early spring rather than fall include:

Can I divide perennials in winter?

Late winter can be a great time to divide perennials. However, soil issues and weather can get in the way of successfully dividing perennials in winter.

In winter, soil is often heavily saturated.  And tramping on saturated beds can lead to soil compaction. This can ruin the rooting environment for our existing plants and our transplants. Also by late winter/ early spring, delicate, new plant growth is emerging. So we are more likely to crush and trample fresh growth as we work in beds this time of year. However, during the annual spring growth surge our beds can usually recuperate from our damage rapidly. So, if we do our divisions in late winter/early spring and manage to crush some top growth, plants likely have the reserves to bounce back in this season and fill out beautifully.

And it probably goes without saying, but if your garden is frozen, it isn’t the time to divide your plants.

Plants to divide by late winter before they begin to sprout & bloom:

  • hellebores
  • Pulsatilla
  • Tiarella
  • goldenrod
  • iris
  • peony
  • many ferns
  • asters
  • lady’s mantle

Are there any perennials I shouldn’t divide?

While most perennials grow abundantly and benefit from being split, some may not.

Trillums, for instance, should be left alone to spread in place. That’s because they’re very delicate and are unlikely to transplant well.

And some plants are near impossible to easily dig and divide. A good example is Baptisia.

Quick recap on when to divide your perennials:

  1. Do you have you have the time to do it?
  2. Is your getting ready to flower or still flowering?
  3. Check the soil to see if it is too moist, not moist enough or just right. (Yes, play Goldilocks.)
  4. Finally, check your most reliable weather source to ensure temperatures aren’t heading for a big freeze.

Everything perfect? Well, get out there and make things beautiful!

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2 comments on “Should Perennials Be Divided in Fall or Spring?

  1. Karen on

    I need to divide crocosmias, iris, daylilies and penstemon. But I’m kind of a fraidy cat. I figure I’ll start with the stuff I don’t care about so much or that is so overgrown that it has stopped blooming. I considered buying a hori hori but was worried my kid would get ahold of it and hurt herself!

  2. rhaglund on

    Seriously, crocosmia, iris and daylily are candidates to divide and give away! They will spread and go mad given the opportunity. I’d be hard pressed to meet someone who has managed to kill any of these during a division session. And, iris left to its own devices will choke itself out and have less bloom. So, go for it.

    And, get a hori-hori! It is the *must have tool* for any gardener. If your kid hasn’t hurt herself with your kitchen knives, do you think the hori-hori will really get her?

    A properly used hori-hori used in tandem with a garden fork will give you gardening super powers!

    Thanks for reading and commenting. Best of luck out there 🙂

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