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.