Bamboo: pruning clumping bamboos

If running bamboos are too aggressive or intimidating, clumping types may be a good way to bring the beauty and utility of bamboo into your garden. Thanks to the structure of their rhizomes, they expand at a slow, measured pace, rather than running anywhere from 5 to 20 feet in a season. They don't require barriers or rhizome-pruning to keep them contained. Clumping bamboos can be virtually maintenance free but, like all plants, they do require some annual care to look their best.

One thing people often overlook is, while clumping bamboos can have a very small footprint at ground level, their arching culms can require a great deal more clearance when allowed to assume their natural form. The best way to deal with this, as with any plant, is to understand its natural growth habit before you plant it and site the plant accordingly. Place it where it will have room to arch out gracefully. It's always easier to work with the natural habit of a plant, rather than fight it. I say this because I've made enough mistakes to have learned that lesson. As you can see in the photo below, my Fargesia dracocephala 'Rufa' arches out almost 5 times wider than its base, and I did not take that into account when planting it. It's begun arching into the the path on the left. Between it and the Parablechnum cordatum (Blechnum chilense) on the opposite side, that narrow path is feeling a bit tight.

If, like me, you've planted a clumping bamboo in a location too narrow for it, there are ways to maintain it. First, the rhizomes can be pruned, as with running bamboos, but without the fear of a missed rhizome sending up shoots 10 feet away next spring. This technique can be used to prevent clumping bamboos from expanding at the base. Mine is still quite narrow at the base, so it doesn't need rhizome pruning. Second, you can prune the culms. The outermost culms can be pruned to the ground, and others can be shortened to create a more upright form. Pruning the culms creates a narrower, more upright plant. This is what I'll show in this post.

Before getting started, it's a good idea to make sure you have eye protection. I've heard about people getting poked in the eye while working with ornamental grasses, and sometimes with trees and shrubs. The same can happen with bamboo. Wear eye protection and be mindful of your surroundings. Don't get tunnel vision and dive head first into a bamboo stake. Besides, you'll look really cool wearing them.

It's a pretty straight-forward procedure. Since this bamboo has such slender culms, I need only a pair of sharp secateurs. Start by cutting the most weeping, outermost culms at the base. I also reached a little into the interior to cut a few culms that were strongly weeping or had grown at an angle instead of straight up. After removing up to about 10% of the outermost culms, you can prune further by topping any other culms that weep a bit. Simply cut off part of the top of the culm, right above a node. With larger bamboos, you can cut off the top 2-3 feet. With smaller ones like this 'Rufa', cut off perhaps a foot. Removing weight at the end of the culm will allow it to stand more upright. Test it by cutting a little off first, then see if the culm is upright enough. If it still weeps too much, cut off another section or two.

As I was working on this plant anyway, I decided to clean up the tiny, dead culms in the interior, as well.

All bamboos should have old, dead culms removed annually to keep them looking their best, except perhaps the ground-cover types, but those can simply be mowed to the ground if they need refreshing. This plant was so small and dense when I bought it, I didn't bother. Now that it's matured a bit, it can be opened up. In the photo below, I've cleaned out one side and bent the culms away to keep cleaning out the other side. This removal of dead culms can now be done annually, and will be a smaller, easier job than it was after allowing them to build up for several years.

As when pruning trees and shrubs, it's a good idea to step back and observe your progress. In the photo below, the bamboo has been lifted enough to be out of the path. I could leave it as is. But it looks a little unbalanced.

After a bit more pruning and thinning, we have a nice, tidy clumper. The ferns and other plants underneath will enjoy having a bit more room and light, and the human occupants of the garden won't feel the bamboo is crowding them on the path. Now I just have to dig out the Chilean hard fern on the other side of the path before it grows into the path. That fern spreads faster than the bamboo.

Pruning this bamboo into a more upright form took only about 30 minutes. It took longer to thin out the dead culms in the middle because I hadn't done it every year. Performed annually, this maintenance doesn't take long, and it's not difficult. I am adjusting to the visual change, particularly seeing the "legs" of the bamboo. With most bamboo, except the ground-cover types, viewing the culms is generally part of the appeal. With 'Rufa', I confess I rather like its natural, weeping form which all but hides the culms from view.

'Rufa' is a wonderful clumper that can be used in the landscape like a mid-sized shrub, generally reaching 6-7 feet tall, potentially to 10 feet tall. It can be about twice as wide, if the culms are left to arch out and weep naturally, though it gets a bit more upright as it matures. Now that you know how to prune it, you can keep it in a narrower space if needed. While easy to maintain in a smaller space, I also think it really shines as an informal, weeping screen or hedge, or planted in an informal woodland setting with space to arch out.

Vigorous yet relatively small and very easy to contain (in fact a good choice for containers, too) as well as tolerating more sun than most Fargesia, it's no wonder this clumper is so widely available. It's one of the best choices for beginners in bamboo, or for those lacking space for larger varieties. 'Rufa' is hardy to USDA zone 5, but performs poorly in the heat and humidity of the deep south. For southern states, dwarf forms of Bambusa multiplex are a better choice for a small clumping bamboo.

I'll end this with the before and after shots next to each other for easier comparison.