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Pruning Shrubs, Part 1 - Why Prune

Learn why you should prune and why you shouldn't prune. Read Part 2

For a distilled version of our pruning articles, check out and download our Pruning Demystified PDF.

Contributors: Stacey Hirvela

What’s the secret of transitioning from a competent gardener to a confident one? Pruning! Though this garden task strikes fear into the hearts of many, it is actually a simple and rewarding process. All you need to do to master it yourself is to understand a few basic principles behind the why, when, and how of pruning shrubs. Once you implement these ideas and techniques, you’ll see a healthier, more floriferous garden that same season. So let’s get started!

Why prune?Home Run Pink

To answer this question, we need to understand what pruning does to a plant physiologically. Plants are genetically programmed for apical dominance. That’s a botanical term that describes the simple phenomenon that plants always want to grow upward. Apical dominance is enforced by the terminal bud – the bud at the end of each stem - which produces a constant supply of hormones that keep the buds below it from growing. When that terminal bud is removed, production of those suppressive hormones ceases, and the lower buds are released. As a result, pruning stimulates a lot of new growth, as multiple buds take over the job that just one single bud was doing previously.

For the gardener, the new growth that results from pruning can accomplish any of the following things, depending on the kind of plant:

  • More flowers. This is especially true for plants that flower later in the season, like roses and butterfly bush. Instead of just the terminal bud producing flowers, all of the lower buds will flower as well, multiplying the effect substantially.
  • Blooming again later in the season. Reblooming plants like Bloomerang® lilac (photo, right) and Bloom-A-Thon® azaleas flower more their second time based on how much new growth they put on after their first bloom. A light trim after they’ve finished their spring bloom means a better show come summer!
  • Brighter stem color. Plants with attractive stems, like Arctic Fire and Arctic Sun dogwood, are the most colorful on stems younger than 3 years old. Pruning encourages the fresh new growth that makes these plants so popular in our gardens.

Pruning may also be used for any of the following purposes:

  • To neaten the plant’s appearance. Some plants, like ‘Limelight’ hydrangea keep last year’s flowers on their stems. These can be cut off in spring to keep the new growth and the current season’s flowers looking crisp and clean.
  • To control the plant’s height and/or spread. Sometimes, a plant that is really too large for the space will have been planted and you will want to prune it to stay a manageable size. And some plants, like Sunshine Blue® II caryopteris (photo, left) and Black Lace elderberry, are capable of becoming rather large plants, but you may want to use them in a flower bed or a smaller landscape that requires some pruning to keep them tight and compact.
  • To rejuvenate an old or overgrown shrub. If you’ve got a very large, very old multi-stemmed shrub on your property, you can give it a new lease on life by cutting it back to short stubs in spring.
  • To remove dead, diseased, or damaged wood. Sometimes branches of shrubs die from weather, from old age, or are damaged by injury or animals like deer browsing them. Pruning is the best way to correct the damage.

Obviously, there are lots of good reasons you might prune a plant, but it’s important to know that pruning is not strictly necessary. No plant dies from a lack of pruning, but plenty die from being pruned improperly! There are plenty of good reasons not to prune a plant:

  • If you are happy with a shrub’s size, looks, and performance, there’s no need to prune it.

You should never prune without a reason. Every other decision you’ll make, like when to prune and how much to prune, will come back to the reason you’ve decided to prune in the first place. If you don’t start with a good reason, you won’t be able to determine what to do next!

Have you made a decision on whether or not your plant needs pruning? Great! Let’s talk about when to do it.

Patent Info:  'Summer Skies' Buddleia PPAF; Golden Glitter Spiraea nipponica 'VERSPI 1' PPAF; Arctic Fire Cornus stolonifera 'Farrow' PP: 18523; Arctic Sun Cornus sanguinea 'Cato' PP: 19892 Can. PBRAF; 'Limelight' Hydrangea paniculata PP: 12874 Can. PP: 2319; White Dome® Hydrangea arborescens 'Dardom' PP: 14168; Sunshine Blue® II Caryopteris incana 'SMNCVH' USPPAF; Black Lace Sambucus nigra 'Eva' PP: 15575 Can. PP: 2633; Show Off Sugar Baby Forsythia 'NIMBUS' PPAF;

438 Readers Rated This: 12345 (3.3)
Anonymous's picture
Anonymous Tue, 05/22/2018 - 4:18pm

I live in an apartment complex on the first floor. The hedges on the side and back of my apartment have grown to a height that is 1/4 up the window. The staff says the landscape company says if they trim the hedges below the window it will cause the hedges to die. Can someone confirm or deny this. I have had hedges trimmed in two of the houses I have owned and the trimming helped fill out the base.

Stacey Hirvela's picture
Stacey Hirvela Fri, 08/03/2018 - 8:54am

It's hard to say without seeing the plants. However, if a plant has not been maintained and has developed a lot of thick, woody stems, cutting it back can cause slow recover and unsightly "holes" to form in the planting. Ultimately, it depends on the species of plant, its care level (ie, regular watering, etc.) and how thick the stems are.

Anonymous's picture
Anonymous Fri, 03/24/2017 - 10:04pm

Google "Pruning" at "extension.virginia.edu/pruning".

Many University "edu" sites have such charts. Check their downloading policy---- many allow at least one copy to be printed for educational use.

Anonymous's picture
Anonymous Fri, 03/24/2017 - 7:29am

My bridal wreath is getting too large for the area, but I would hate to lose it. Can I prune it back a bit without losing too much of it's natural look and when is a good time to do this?

Stacey Hirvela's picture
Stacey Hirvela Tue, 03/28/2017 - 6:44am

Yes, you can prune your bridal wreath spirea. The best time to do so would be immediately after it finishes flowering this spring. Generally speaking, you should prune it by removing entire stems at the base or where they connect to a large stem - avoid simply cutting back the branches, which will interfere with its natural habit.

Anonymous's picture
Anonymous Thu, 09/08/2016 - 5:41am

When should I cut back my grasses, some day in spring and others say in fall, what is the best. Time?

Anonymous's picture
Anonymous Sat, 03/25/2017 - 2:55pm

Some grasses are very pretty with their cat tail end so I leave my grasses for cutting back in the spring before I see new growth emerging.

Kerry Meyer's picture
Kerry Meyer Fri, 09/09/2016 - 2:41pm

It really depends on the grass. This article covers the ins and outs:  https://www.provenwinners.com/learn/did-you-say-use-chainsaw

Warm season grasses should be cut back in Fall or by Mid to Late Spring.

Cool Season Grasses should be cut back in very Early Spring

The article has more in depth information.

Anonymous's picture
Anonymous Sat, 06/25/2016 - 1:15pm

I am hoping you or someone can please help, as I am a beginning gardener. My landlord and I planted some shrubs in the yard in mid May, about 1-1/2 months ago. He torched some weeds near the bloomerang lilac, yellow potentilla bush, and magic carpet spirea, and now they all have a bit of heat and fire damage on some branches and leaves. The poor babies!! I saw on one website that sometimes it is best to leave the bush alone and see how it does until fall, early winter and then prune when dormant. Is this correct? Or should I prune off any branches that have the heat and fire damage now? Will this further stress the little darlings? Please help! I chose them all with such great care and enthusiasm, I don't want to lose them. Thank you. Carrie.

Stacey Hirvela's picture
Stacey Hirvela Mon, 06/27/2016 - 12:02pm

I'm sorry to hear that! I would definitely not prune anything now. Even though it may be a bit unsightly, it's really best to let the plant show you the extent of the damage. The foliage that was burned will probably drop, but that's not a cause for concern. Just keep your plants free of stress by keeping them well-watered, making sure the soil is well drained, and protecting them from further damage, whether by humans or rabbits. If no new growth emerges from the area next spring when the plant starts leafing out, then you can prune those portions off.

Anonymous's picture
Anonymous Wed, 06/22/2016 - 11:00am

I plated two hydrangea and all the flowers are mostly dead. Do I remove all dead flowers.

Stacey Hirvela's picture
Stacey Hirvela Fri, 06/24/2016 - 1:02pm

If you'd like to, you may - it's up to you. If you do want to cut them off, cut just above the point where a set of two full leaves are emerging.

Anonymous's picture
Anonymous Sat, 04/09/2016 - 8:33am

We have five barberry in a row--three are larger and were planted first. Two are smaller and were planted later. Can I spring trim the older three to be a little smaller in size to even out the row? I live in Zone 4B (Wisconsin).

Stacey Hirvela's picture
Stacey Hirvela Wed, 04/20/2016 - 5:01am

Yes, you can definitely prune your barberry. I would wait until after the new growth has emerged and hardened off a bit before doing so - I'd guess in Wisconsin, late May would be the best time for it.

Anonymous's picture
Anonymous Fri, 04/08/2016 - 6:40am

What should I do about overgrown boxwoods? I am afraid that pruning will not bring them back to a manageable size. I would rather not have to take them out of my landscape. Should I try to prune them?

Stacey Hirvela's picture
Stacey Hirvela Wed, 04/20/2016 - 5:00am

I would not recommend severe pruning of boxwoods - they will take a very long time to recover. I would try to prune them a little bit at a time over several years rather than trying to do one extreme cut back. We'd be happy to offer more specific guidance - contact us here: https://www.provenwinners.com/feedback (select "shrubs" as the category) and I'll tell you where you can send a photo, which would help us address your situation more directly.

Anonymous's picture
Anonymous Fri, 04/08/2016 - 5:59am

This is a very informative article. I just received my catalogue from proven winners & it has some creative ideas. Thank you

Anonymous's picture
Anonymous Thu, 04/02/2015 - 1:27pm

I have several that I have inherited on the property of my parents. I do prune them after they bloom. I was told to prune the new growth to shape them. However, several are kind of dead on the backs of the bushes and several seem to have lot of dead wood in the middle. they are about 8 years old. We have very poor ground in the mobile park. How can I get them to be full and not have so many dead branches? I have given them azaleas fertilizer also after they bloom. Please advise what exactly do you do with them.

Stacey Hirvela's picture
Stacey Hirvela Mon, 04/13/2015 - 9:07am

Go ahead and prune out all of the wood that you know is dead - this will help you see what you are left with, as well as help bring light and air into the center of the plant, which should encourage new growth to form. To get a lot of new growth on the top of the plant, you'll need to create an environment that fosters healthy root growth, as the top can only grow as much as the root system can sustain. To encourage better root growth, I would recommend applying a 2-3" thick layer of mulch (shredded bark, compost, or pine needles are all good choices) and watering the plants regularly. Fertilize them in early spring each year. This should get them back on track to lush growth and vigorous flowering.

Anonymous's picture
Anonymous Wed, 11/06/2013 - 6:31pm

Thank you so much Stacy for a very informative lesson.
I've known the "WHAT" of what happened when you cut off the end of a branch or stem, multiple stem growth and/or blooms, however no one ever explained the "WHY".!!
Very informative article and I'm looking forward to more!!
Again, thank you and PW for as ever, excellent information!! t.w.

Anonymous's picture
Anonymous Fri, 04/12/2013 - 9:38am

It would be nice to have a chart...by variety and when to prune...spring, summer, fall, winter...before or after bloom
thanks
Carol

Anonymous's picture
Anonymous Sun, 03/29/2015 - 12:37pm

Pruning chart? You bet, I would love one also. Chart showing crepe myrtle, sonic boom weigela, Little Henry, Happy Face , butterfly bushes (dwarf), Rose of Sharon, and so on. Always, always, have questions about correct pruning. A chart of some sort would be fabulous!

Anonymous's picture
Anonymous Sun, 09/14/2014 - 7:06am

Would love a pruning chart.

Anonymous's picture
Anonymous Tue, 10/15/2013 - 12:43pm

I would like that too!!!!

Anonymous's picture
Anonymous Sat, 10/12/2013 - 5:39am

I agree with Carol
It would be nice to have a chart...by variety and when to prune...spring, summer, fall, winter...before or after bloom
Elbee

Anonymous's picture
Anonymous Fri, 10/11/2013 - 2:32pm

Totally agree about the chart. This would be very helpful.

Anonymous's picture
Anonymous Tue, 04/02/2013 - 3:49pm

This was so informative. Thank you for taking the fear out of pruning. Look forward to the next article.

Anonymous's picture
Anonymous Tue, 04/02/2013 - 8:54am

awesome info, can't wait till the next part
enjoyed for sure
I always get nervous when it comes to pruning
very helpful

thanks
Tammy

Anonymous's picture
Anonymous Sat, 03/30/2013 - 8:17pm

Allot of good information. I can not wait for the rest of the series. I am hoping there will be info on pruning apple trees.
Thanks for the excellent article :-)

Nadine Noseworthy
Fenelon Falls, ON
nmnoseworthy@yahoo.com

Anonymous's picture
Anonymous Tue, 10/29/2013 - 7:29am

Yes prunning apple tress info would be nice. Also Bing cherry and plums.

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