When’s the Best Time to Cut Back Perennials in Colorado and Similar States?

by | Updated: Nov 10, 2022

When to cut back perennials in Colorado

It’s tempting to want to get out early in the fall and tidy up your western garden for winter, especially if you’re having a mild fall. But is it too early? When’s the best time to cut back perennials in Colorado and similar states?

In this article, you’ll get the scoop on:

  • Why it helps to wait before trimming down plants in the fall
  • Whether it’s better to cut back perennials in the fall or spring in Colorado (hint: it depends!)

Let’s start with your garden in the fall…

No need to rush it. Put your feet up. Enjoy the fall color!

Your plants will thank you for it.

On autumn days, it may look like your perennials aren’t doing much. But they’re doing A LOT… under ground.

In the fall, soil temperatures are still warm, and air temperatures are cooling off. For most plants, these are ideal conditions for growing roots.

And healthy roots are the secret to bigger, stronger plants next season, which is so important in our gotta-have-some-moxie West.

So, don’t cut back your perennials too early, especially if they’re still green.

Instead, let them gather as much energy as they can for their roots, so they can come back strong and showy in the spring.

Wait until you’ve gone through several hard freezes before you get out your pruners. (A hard freeze is when temperatures drop to 28 degrees or below.)

When temps start dipping and dancing their way into the mid-20s, you’ll likely see the leaves on your perennials wither, brown, curl or drop.

That’s your cue to prune IF you want to cut back your perennials in the fall.

Of course, then the question becomes…

Is it better to cut back perennials in the fall or spring in Colorado and similar western states?

The short answer is: It depends.

Mama Nature likes to keep us on our toes!

Let’s assume, for a sec, that you don’t live in an area that’s at risk for wildfires. There are lots of good reasons to wait until late March or early April to cut back most perennials, including:

  • Giving your landscape winter interest and texture.
  • Helping your plants survive our weird winter weather, especially your newly-planted perennials, your “marginally hardy” plants (plants that are “iffy” on whether they can survive winter where you live), and woody, thick-stemmed plants like lavender.
  • Feeding birds and providing homes for overwintering baby bees and pollinators. The Denver Botanic Gardens has a helpful article on this topic.

But there also are some scenarios when fall clean-up is valuable. For example, it’s a good idea to cut back your perennials in the fall if you:

There is no one-size-fits all approach to western garden clean-up.

What I do in my Colorado perennial garden

When I first moved to Denver, I used to cut back my perennials in the fall. I left my flowerpot clean-up until the spring.

Now I do the opposite. 

I tackle my flowerpots in the fall. Here are 5 reasons to empty your pots in the fall in the West.

And I wait until late March and early April to cut back the majority of my perennials. I wait until I see new growth appearing from the ground.

Because native bees often nest in plant stems, I set aside the plant stalks once I trim the plants down. Some bees don’t emerge until later in the spring.

Why not clean up the garden earlier, like in the late fall or in February?

Two reasons:

  1. Unpredictable Colorado weather. I’ve learned the hard way that we tend to bounce back and forth between winter and summer… in the winter and early spring. Big temperature swings in February, March and April can be tough on our plants. I leave last year’s growth on the plants as long as possible to give them as much protection as possible.
  2. Pollinators. Many bees that are nesting in plant stems and under leaf debris aren’t ready to emerge that early.

Related topics that may interest you:

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Ann from Go West Gardener with her flowerpots and garden

Hey there, I'm Ann

I’m a Certified Colorado Gardener, published western garden writer and dog mama. I help flower gardeners in the intermountain west skip the “Why didn’t anyone tell me that phase?”, so they can get pretty results faster. More about Ann >>

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