You've clearly put a lot of thought into this, but all of those ideas have problems, particularly over the long term. In addition, that is a pretty shallow trench to contain bamboo: at least 20"-24" deep would be much more failsafe.

Here are your two best options:

1. Deepen the trench, and then fill it with sand. Then, twice a year, use a sharp shovel to probe the sand to see if any rhizomes are attempting to escape, and remove any you encounter. The downside of this is that you have to remember to do the biannual maintenance.

2. Deepen the trench and install bamboo barrier, which is a thick, hard, roll plastic that will conform to your curves and block rhizome escape. You position it in the ditch and then backfill with soil, letting the barrier stand above the ground level by a couple of inches. The best price I know of is at Lewis Bamboo, and it costs -- with free shipping -- about $2 per linear foot for 60 mil material that is 24" high:

Bamboo barrier

You can buy a special clamp to lock the two ends of the barrier together, but I just overlap the ends tightly by about a foot and have had no problems

I doubt that I will use the "sand-filled-trench" idea. I cannot see myself digging up the sand twice a year. This simply won't happen.

Thanks for reminding me that the thick plastic barrier is still an option. Actually that was something I thought of doing almost 10 years ago, and I still had a big roll of that thick plastic barrier in my garbage that I purchased from one of the bamboo web site. Now I may need to remove dusts from it and see if it may be a good idea this time around.

At that time, I decided not to use that thick plastic barrier. My plan was to enclose the entire bamboo area with the barrier. But this would require me to dig very deep near a fence with my neighbor. I was afraid that this might weaken the base of the fence and might cause property damage. That's why I didn't use it despite the fact that I had paid for it.

Now, I may need to use a "hybrid" approach: Keep the opened trench in the area near the fence, and use the barrier facing the lawn. That may work. Given the fact that I have already purchased the barrier, I may as well use it. I read some horror stories in this web site about bamboo rhizomes that are so stronge that they could puncture the barrier. I figure my area has cold winter and dry summer. The bamboo rhizomes should not be that powerful in this area, and the barrier should be able to keep the bamboo rhizomes under control.

Having said this, I still take a "wait and see" approach to see if there are other suggestions that I can use to stiffen the open trench because that is my first choice. The 1-foot deep open trench should be more than enough to contain the bamboo in my backyeard. During the course of digging the trench, I only found two bamboo rhizomes that were at the depth of 10-inches. In one case bamboo rhizomes was densely packed together, and new bamboo rhizome had to go deep to get out. And in another case, bamboo rhizome was blocked by tree root (of a tree that was recently cut down) and had to go deep to grow around the tree root. Otherwise, 99% of bamboo rhizomes were within a couple inches from the surface. Actually all the newly grown bamboo rhizomes that were sticking out in the open trench were just a couple inches below the top surface. Therefore, in my situation, a 1-foot trench is more than enough. And the open trench is still my first choice.

I am still hoping that there is a way to stiffen the trench.

Jay C

Thanks for the additional info. This seems like plastic barrier is a good product. But that will be my last resort. I still prefer the open trench method.

The open trench should stop 99% of the bamboo rhizomes in my backyard. It may not be able to stop that 1%. But I don't worry too much about that 1%. This is just like weeding. I don't expect to remove 100% of the weeds. I am happy just to get rid of 80% of the weeds. I have lived with bamboo in my backyard for many years. I have a high level of tolerance. If that 1% pops up in the middle of my lawn, I know exactly what to do with it.

Please note that when I asked for a way to stiffen the trench. I am not asking for something that is so strong that it will prevent the bamboo rhizomes from getting through. I am asking for a way to prevent the trench from collapsing -- from foot traffic or from rain. This has to do with keeping a nice "edge" in my lawn.

Please let me know if any one has any suggestion about stiffening one side of the trench to prevent it from collapsing (from foot traffic and such).

Thanks.

Jay C

If you are willing to live with an open trench and can maintain it, it sounds like it will work for your purposes. My main concern with an open trench would be someone -- a child perhaps -- walking around in the yard and breaking an ankle.

If you want something sturdy to support the trench, stacked lengths of treated 4X4 posts with the ends pinned with rebar would be my choice. To make life easier with your project, could you do some rework and dig a rectangular trench?

Thanks for pointing out the possible danger of someone may mistakenly step on the open trench. I didn't think of that. Seem like using the hybrid approach is getting more and more appealing. Having the heavy thick plastic barrier facing the lawn can minimize the problem of someone mistakenly steps into the open trench (and avoid the problem of the edge of the trench collapsing) while keeping the open trench in area away from the lawn to avoid digging deep near the neighbor fence. Seem like a good trade off. I will consider about this.

Yes, the 4x4 posts with metal rebar sounds good. I just have to turn any curve into 3 or 4 straight lines. I will also consider about this idea. Thanks for the great suggestion! I appreciate that.

Jay C

That sounds like a clever hybrid solution. Good luck with your project.

I too went with the "hybrid" solution 4 or so years ago, more so out of laziness with not wanting to dig 22" down for another 70 feet along the front of the plot lol.. I installed a barrier (HDPE) along the rear and went with a pruning trench in the front about 12-16" deep (same idea as you). I planned on filling it with sand but just never seemed to get around to it, resulting in the same issue with erosion. After the second year I found it to be more work than it would have been if I just installed the barrier. Last year I decided to scrap the trench, rented a trencher ;) and just installed some 60mil along the front as well. Luckily I did, as in the process of installing the barrier I found a half a dozen or so stray Aureocaulis rhizomes that snuck by the trench; I measured them at 25" deep. I think you'll too find the trench to be more work than it's worth, although it is a healthier option for the boo as the root pruning keeps them from getting bound as quickly as they would with a barrier.

michael-

Rhizomes 25" deep is amazing...and disturbing :-(

You found rhizomes 25" deep. This is indeed very disturbing. Which "zone" do you live? I am wondering if this has to do with how warm and wet where you live.

Definitely disturbing! haha, it has me questioning the efficacy of my barrier at 22-24" .. I now cross my fingers and keep an eye on my neighbor's lawn when it comes shooting time .. I have very loose sandy loam here in Connecticut - Zone 6b; making it easy for them to dig a little deeper I'm sure..

Mine is also in zone-6. And my soil is very sandy. However, I don't water my lawn that often. This is bone dry 6" down. I doubt the bamboo will want to go deep to look for non-existing water.

I am wondering if you saw shoot coming out from the deep-running rhizomes. They would have to come up somehow, right?

They weren't developing any shoots (at that time), and they'd probably make their way back to the surface before they would waste their energy trying to shoot from so deep, but who knows.. I do have a drip system set up on that plot, as I interplanted with Nigra and wanted to keep them happy for the first few years.. So they do get their fair share of h20, no reason to search, strange really..

Yea I had actually read a while back that a good method for controlling spread to where you'd like is to water liberally on the desired location of new shoots, for instance: if you wanted more growth on the northern "side" of the planting you'd water more on that side and withhold on the southern. This would be kind of hard unless the grove was under cover of some sort but the theory makes complete sense.

What puzzles me is that I was giving them at least 2" a week and plenty of milorganite; wonder what they're searching for...? lol

I've given up on trying to out-think my bamboo :-)

I grew bamboo in my riverside garden in France, when I lived there. The first year, very little happened; the second, we had quite a lot of strong shoots, which began to give the area shape and definition; the third year I had to contact the Paris Senate to see whether they would let me take over the country to accommodate the spread of the bamboo....