How Small Can I Prune My Shrub or Tree? A Rule of Thumb

This is a question most of us pros have come to dread. Not because we dislike answering questions, but because the subtext is so often, “I want a particular tree, but I don’t have room for it. May I have your professional go-ahead to hack the holy hell out of it to keep it to size?”

The answer is no. We love you and want you to be happy, but no.

If you have to hack the holy hell out of something to keep it a reasonable size and shape for your garden bed, then nobody is going to enjoy the process.

Not you, who needs to get out there to prune every eight months.

Not your plant, which will begin to create crazy long shooty growth in response to being hacked, and will eventually get aphids or just develop a terrible form from being pruned in such an unfortunate fashion.

And not your friendly local gardening professional, who will cringe every time they drive by and see the poor plant struggling unsuccessfully to fit our human expectations of how big it should become.

Rant over. Now here’s a helpful rule of thumb:

In general, you can keep a plant pruned 1/3 smaller than the tag says it will grow.

So if the plant tag says:

  • 10 feet tall by 6 feet wide, read that as a minimum mature size of 6.5 feet by 4 feet wide
  • 12 feet tall, read that as minimum 8 feet tall
  • 15 feet tall, read that as 10 feet tall
  • 20 feet tall, read that as 13.5 feet tall
  • 25 feet tall, read that as 17 feet tall

That is truly the limit on how far down you ought to prune, and even then you’ll need a modicum of pruning skill to make that happen in a graceful way (check out this book if you need help and advice). But yes, in general, you can keep a plant 1/3 smaller than it wants to eventually grow, without sacrificing the flowers, growth habit and character that made you want to plant it in the first place.

If your plants don’t fall within that 1/3 limit, I’d definitely advise that you select a different plant for the spot, or even be willing to remove a plant if it becomes clear it’s wanting to grow far larger than the space you have for it.

It can really ruin the feelings you have for your garden when you are tied to an endless cycle of too-often pruning, or when you have to look at a shrub that vacillates between overgrown and heavily pruned. Particularly if it’s a plant you have a special affinity for.

There are so many gorgeous plants in the universe, it’s way better to get creative and choose one that will thrive in the space you have for it.

Further reading:

How far apart do I plant things?


15 responses to “How Small Can I Prune My Shrub or Tree? A Rule of Thumb”

  1. Laughing – love your rant! And a very good rule of thumb, it’s nice and easy to remember.

    When I finally get around to doing a resource page, I’m going to link to this as I think that rule and your Hydrangea pruning video are really helpful. It’s so much easier to see pruning being done than trying to describe it!

    • Aw, thanks Rachel! There are already about three other pruning “rule of thirds” that I can think of, so one more seemed like a good plan! LOL. I’d be honored if you linked over sometime in the future! And I am intrigued by your garden design programs. I know a lot of people who would enjoy and benefit from something like that!

      • I’m always happy to point people in the direction of good resources, so it will be my pleasure!

        Well, if you would like, I’d be more than happy to give you a review copy of one of the courses so you can see what you think. Version 2.0 is coming out soon, so let me know if you’d like to take a sneak peek before I release it.

        • Rachel, I’d love to take you up on that! I’m feeling a bit slammed at the moment, but let’s talk after the holidays, as it seems a great match. Maybe there’s potential there to give a class away to a reader as well? Let’s talk. I know what you do on your blog is stellar, so I can only imagine what you can share in a full course.

  2. I like this post. Here, people ignore the tags even and just plant wherever all the time. I’m also glad there are lots of dwarf varieties of plants available that makes it easier to fit cool plants into smaller landscapes.

    • Liz, they do that here, too! 🙁 The worst part is that we all become so sentimental about living plants that it’s hard to convince people to remove a mature shrub or tree, even if it has gotten into a cycle of “prune to sticks, then it’s overgrown, then prune to sticks again”. It’s a toughie. It’s nice to have a rule that acts as a good cutoff point so we don’t (I include myself in this) rationalize a too-big plant with the old “I’ll keep it pruned” chestnut.

  3. So true! With the HUGE selection of dwarf and miniature conifers alone, one should find something they could fall in love with for the available space in their garden. I do like you mentioning that people could also be willing to grow a plant for a number of years and then replace it if it becomes too large. Our garden plants to not need to be forever in our garden – if it doesn’t work out, it will make good compost. Then again, good planning and plant selection can alleviate the problem in the first place. Great post!

  4. Yes it would be wise to at least trim the lower leaves to avoid diseases but other then that there is no particular science. I think the confusion lies in the fact that newbies think they will end up doing it wrong or kill the plant.

  5. It is a fair comment that you cannot fight the nature of the tree or shrub but you can work with it to create the desired effect you are seeking. It is also important if you are planning to do something other than let the plant achieve its natural size and form to start when the tree or shrub is small and direct/manipulate the growth as you wish. Espalier treatment is a good example.

    I am also sure this is climate dependent as well but take for example a white spruce or colorado spruce. by starting small and reducing the candles in June by even up to 2/3’s you can create a dense specimen and restrict the ultimate size or you can form this into a hedge if you wish.

    The key is to know what you want to achieve, know the types of cuts that will do this and start when the tree or shrub is small.