Thin running bamboo after the new shoots harden. Cut the oldest culms at ground level, and leave at least two-thirds of the live grove.
Thin the oldest culms after the new shoots harden
| Factor | Recommended | Avoid |
|---|---|---|
| When | After new culms have hardened, usually late summer; or just before the next spring flush | Do not walk the grove while tender shoots are still pushing |
| What to cut | Dead, damaged, and the oldest dull culms, flush at the soil | Do not leave tall stubs that trip people |
| How much | No more than about one-third of the live culms in one year | Do not strip a screen to a handful of canes in one day |
| Screen | If you shorten a cane, cut just above a node | Do not shear the tops like a boxwood hedge every month |
Each culm reaches its full height in the first season and does not thicken later. Older culms strengthen, then turn brittle as the grove replaces them. [1] Wait until you can see the new canes clearly. Thinning while shoots are still soft is how you snap next year’s screen. [2] Sun and the yearly rhizome check stay on How to Grow Running Bamboo.
When do I thin the culms?
After new culms harden, usually late summer, or just before spring shoots. Do not thin while tender shoots are still coming up.
How to thin running bamboo
Mark the oldest canes, cut them flush, and stop when you have taken about a third of the live grove.
- Wait until new culms have hardened, usually late summer, or thin just before the spring shoot flush. [3]
- Mark dead, damaged, and the oldest dull culms. black bamboo and moso take the same cut at grade.
- Cut flush at the soil with a pruning saw so you do not leave a stub to trip on.
- Stop when you have taken about one-third of the live culms. The grove needs the remaining leaves to push the next round of shoots. [4]
- If you shorten a cane for a screen, cut just above a node so the stub does not die back.
How much of the grove can I cut?
Do not take more than about one-third of the live culms in one year. You can remove every dead cane with no foliage.
What fails when you prune
A hard shear in spring, while new shoots are still soft, is the main reason a grove looks thin the next year. Taking more than a third of the live canes in one day starves the rhizomes. A hedge-trimmer pass that leaves ragged tops above a node dies back and looks worse than a clean cut.
Can I shear it like a hedge?
One shaping after the new canes reach height is fine. A monthly shear is not how this grass grows. Cut at a node, or cut the whole cane at the soil.
If new shoots have already hardened, thin this week — waiting until the next flush is how you step on tender canes.
FAQ
When can I start thinning a new planting?
Wait until the grove is established, often the third to fifth season. A new plant needs every leafy culm.
Related guides
Recommended plants
References
- [1] Wilson Bros Gardens -
https://www.wilsonbrosgardens.com/how-to-prune-bamboo-plants.html - [2] Bamboo Garden -
https://www.bamboogarden.com/resource-pages/bamboo-grove-maintenance-thinning - [3] University of Maryland Extension -
https://extension.umd.edu/resource/containing-and-removing-bamboo - [4] TerraBamboo -
https://terrabamboo.com/bamboo-lifespan/
This note is part of Phyllostachys Guides.
More pruning timing notes by plant live in Pruning Guides.
Updated: Reviewed by Bosquelle Editors