Trimming bamboo is useful if you have any kind of bamboo screening or hedging that is perhaps a bit untidy or straggly and you are looking for a way to tidy it up and promote the growth of more branches and leaves to make it denser.
Bamboo doesn't need very much trimming to get it into a better shape and provide a more functional screen or windbreak, or just to show off the lower part of its beautiful culms.
If the bamboo is leaning, or looking a bit thin and untidy, you can cultivate a more hedge like function through pruning.
Trim bamboo in the winter if possible, when it has stopped all growth for the year, or during the early part of spring before it starts the new season's growth.
If you want to reduce the height of your bamboo, you can cut the culm just above a node to encourage more growth from that node. I found that this method of trimming bamboo produces new shooting branches from the node below where you made the cut.
Each new bamboo branch tends to grow upwards from the node but thinner than the culm it is growing out of. The new branches will grow leaves with the result of a more hedge like appearance, although this may not happen until next season depending on what time of year you trim the bamboo.
I cut some older culms from the hedge in the photos on this page right down to just above the first node visible above ground.
As you can see it resulted in a lower bushier hedge sprouting from the cut culm, most of the culms had two branches coming out from the node but a few had three (I'm not sure if that number would vary among some species).
I also cut some of the older culms a bit higher up in the following year to achieve new bamboo branches at a higher level. This resulted in a kind of two tier looking hedge with thick foliage at different levels.
You can see the new culms that grew from the roots last season towering above the previously pruned culms.
All I have to do now if I want to continue with a lower hedge height is to cut last year's complete culms down, either to the node above ground or to anywhere in between that I want new branches to appear. Or I could just leave the tall ones and maintain a three tier hedge so I still have the full height.
I purposefully did not cut all the culms down in one season as I did not want to take all the energy away from the bamboo at once and preferred to leave some screening there while waiting for the new branches to appear.
Once you have cut off a culm its growth will stop and it won't grow higher. New growth from any cut culm will be weaker than the original culm.
You can use this method for thinning out clumping types of bamboo species that grow new culms each year in the summer months.
Removing older culms from the middle of the clump will tidy it up and thin it out to display the younger and better looking culms. It is also a good opportunity to take out any culms that have a bad shape or look weak and unattractive.
Cut culms out either in the spring or winter when the bamboo is not in its growing season. Do be careful not to tread on any new shoots just coming up out of the ground when you are working on this in the spring otherwise you will damage them.
Any new culms that grew late in the previous season, such as during the autumn, may not have grown leaves at the time but they will grow in the spring when the weather warms up again. Don't trim these autumn grown young and leafless culms because they haven't had a chance and it may kill the culm or damage the health of the main plant if it's not well established.