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6 Perennial Pruning Mistakes To Avoid At All Costs

I’ve confessed it before, and I’ll say it again. No matter how much gardening experience I’m accumulating, I’ll always find pruning slightly intimidating. There’s something slightly unsettling about cutting off healthy plant material; oftentimes, it triggers the “what if you’re making a mistake?” response in my brain. 

Incidentally, I have the same reaction before getting a haircut, maybe because it feels just as permanent.

Lucky for me, neither haircuts nor pruning are permanent. Things grow back. Anxieties get squelched. And I learn from my pruning mistakes just as much as I learned from that misshapen bob haircut that aged me two decades in twenty minutes. 

Here’s what to avoid when you’re pruning perennials. (I wish I were just as confident dishing out hair styling advice.)

1. You’re pruning at the wrong time of year.

Hands down, the most common perennial pruning mistake I keep seeing in other people’s gardens. (And one that I used to make when I first started gardening too.)

I noticed it usually goes hand in hand with the “fall cleanup” mindset. It certainly did for me more than ten years ago, before I learned of my mistakes. Over time, it’s not only detrimental to the health of the plants but also to the ecosystem of the garden. 

Rudbeckia seeds are a good source of food for birds in the winter.

Let me explain. 

Not all perennials need to be pruned in the fall. In fact, for most perennials, you should wait until spring before you bust out your secateurs. Have a look at this list of fifteen common perennials that you should only prune in spring

There are so many advantages to letting perennials overwinter in place: 

  • They provide food and shelter for wildlife during the winter months;
  • The dry foliage acts as an insulator for the crown of the plant when it’s cold;
  • And most of them are just downright beautiful in a winter garden. 
Lunaria (Honesty or silver-dollar plant) adds so much charm to a winter garden.

So often, I see perennial grasses – whose main appeal is adding winter interest – being chopped down in November. I swear, if I wasn’t an introvert, I might start knocking on these people’s doors to tell them they’re wasting their money buying winter grasses if they’re going to raze them in the fall.   

Then there’s the downright insanity of cutting off next year’s blooms by pruning in the fall. This is a danger for perennial shrubs that set next year’s flowers on this year’s growth. So if you’re thinking of cutting rhododendrons, azaleas, magnolias or forsythias in the fall, think again. 

Rhododendron in February, full of buds. If you prune in the fall, say goodbye to any flowers.

Then there’s a flipside to this rule. Some perennials will benefit from fall pruning, such as peonies, bearded irises and Japanese anemones that don’t usually overwinter well. Have a look at this list for more ideas, including some of the scenarios when you should cut these perennials down before winter.  

2. You’re skipping pruning altogether. 

I’ve made this mistake time and time again when I couldn’t bring myself to cut down perfectly good growth. I’ve skipped pruning my clematis one year because it looked so flimsy, I just couldn’t believe it would ever bounce back. 

Do you know what happened? The following year, the growth just started from where it left off, and the whole vine was scraggly and struggling. (Luckily, now I have a good system for figuring out when to prune my clematis vines, depending on the group.)  

It can be hard to tell where to prune clematis.

Not pruning perennials at all can have a few different consequences. 

If it’s the kind of perennial that dries up throughout the winter months – say, rudbeckia, echinops or echinacea, then the new growth might end up impeded in the beginning by the dead plant material. It won’t hurt the plant per se, but it might end up with fewer blooms and less robust growth. You need to make room for fresh growth. 

But an unpruned clematis leads to straggly growth.

If it’s shrubs or vines we’re talking about – such as most cultivated roses or clematis – not pruning them will result in weak, scraggly growth with fewer flowers comically high up the plant. 

Similarly, perennials such as peonies, daylilies and Japanese anemone need a fall pruning simply because they don’t overwinter like more fibrous plants do. Instead, they’ll often turn mushy and soft after a hard frost. This moist and dark environment is more likely to harbor unwanted fungal growth.

Peonies don’t overwinter well at all, so you can’t skip pruning.

3. You’re pruning too much (when you shouldn’t)

I hope my previous two points don’t sound all doom and gloom. Most perennials are pretty forgiving of wrong pruning, both in terms of when we do it and how much of the plant we remove. 

They’ll grow right back – albeit sometimes slower and later in the season. But they will rise again. 

A Santolina plant that has been over pruned way too deep down the stem.

However (you knew there would be one, right?), cutting too much off some woody plants, such as rosemary, santolina or lavender, is one serious pruning mistake. Especially if you’re cutting into old, shrubby wood that won’t send out new growth. (Here’s a simple guide to pruning lavender, while we’re at it.)

Cutting off the stems down to ground level can be a source of stress for plants such as roses. It won’t kill them (except in a worst-case scenario), but it might set them back a couple of years. 

If in doubt, prune less, but do it more often. 

4. You’re doing hard pruning when you should only be thinning.

Some perennials – especially flowering shrubs such as rhododendrons, magnolias, camellias and some hydrangeas – are simply slow growers that don’t require much pruning. They do need thinning or deadheading, but nowhere near as drastic as hard pruning. 

The tulip magnolia shrub gets a thinning after the flowers are gone.

In fact, I recently had to thin out my tulip magnolia shrub to open it up a bit and allow more airflow in. If I had pruned this shrub hard, it would have taken a year or more for it to recover. But because I only thinned it out, there’s no harm done.  

5. You’re pruning too late or too early in the year. 

This pruning mistake can damage perennials that put out new growth immediately after getting a trim. 

A classic example of this would be roses. If you prune them too early (in my gardening zone, that would be from mid-October to early November), they might respond by sending out fresh growth. That’s the last thing you want on your roses before the first frost of the year. 

The same reasoning applies to pruning perennials too early in the year. 

And I don’t mean just roses here. Remember that dry and dead plant material acts as a self-mulch, a sort of insulation that protects the crown and the young shoots underneath. If you remove this insulation too early (for me, that would be February and the first half of March), you’re removing a layer of protection when the danger of deep frost is not yet in the rearview mirror. 

6. You let your healthy prunings go to waste.

Ok, I admit this is not so much a mistake as a possible oversight. It’s also a realization that I’ve had fairly recently, so I’m very keen to share it far and wide with our readers. 

Turning prunings into cuttings feeds two birds with one scone. Take the healthy plant material that you’ve removed via pruning and stick it into a pot. With a bit of aftercare, it will root and make more plants. 

It sounds simple enough, but there are a few prerequisites to pay attention to if you want to really increase your rates of success. 

Spirea cuttings that I took when I pruned the shrub in the fall.
  • Always root healthy plant material. If you’ve removed dead, diseased or damaged parts, don’t use that for propagation.  
  • Some plants root better from softwood cuttings, others from hardwood or semi-hardwood cuttings. Some perennials will propagate well from both types of cuttings, but softwood requires more patience and care. 
  • Lastly, don’t forget the aftercare needed for a successful propagation. Keep the cuttings well watered but not too soggy. And if you’re propagating from fall prunings, remember to take the cuttings to a sheltered spot if it gets too cold. 

Here’s a list of perennials that you can propagate from cuttings in the fall.  And if you’re reading this in spring or summer, here’s a list of thirty perennials that you can propagate from softwood cuttings

Don’t let my warnings scare you away from pruning perennials though. It’s something that you can’t avoid as gardeners, so we might as well do it right. 


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Mickey Gast

I like to think of myself as a writer who gardens and a gardener who writes. I was hooked into this lifestyle more than a decade ago, when I decided that my new husband’s tomato patch had to be extended into a full-blown suburban veggie paradise. It was a classic story of “city girl trades concrete jungle for kale jungle.”

Before that, it was a humble peace lily that gave me the houseplant bug, so I have her to thank for 15+ years of houseplant obsession. I get a kick out of saving and reviving houseplants that others write off, although my greatest sin is still overwatering.

When we went back to renting in cities, I gardened in community gardens, campus gardens and post stamp-sized balconies. Setting up gardens from scratch in three different (micro)climates taught me to stay humble and to always keep learning.

Nowadays, when I’m not writing, you’ll probably find me pottering around my suburban backyard where I’m creating a pollinator paradise, complete with herbs, veggies and flowers.

If you’re nosy like me, you can follow my plant experiments on Instagram @greenwithpurpose. I also write about plants, gardens and books on my website, GreenWithPurpose.com
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