Eco-Answers from the Pros: Controlling Invasive Bamboo

I live in north central Arkansas and have an issue with an invasive plant. There is a large stand of running bamboo along my back fence line that is expanding at the rate of 5-10 feet per year. It was on my neighbor’s land and he refused to take it out. I recently bought a few acres from this neighbor and now own the land with the bamboo. It is several decades old and very tall. I have already mechanically removed a large stand of plants the same size on my side of the fence line by digging out almost everything and then making two more passes over the last two years. It’s now eradicated.

What is the best time of year to take this other stand out, in terms of soil and wildlife disturbance? I see a lot of birds flying in and around the bamboo, and the mechanical removal does disturb the soil a lot. I was planning to do it in early February when the bamboo may be dormant, but would it be better to do in late fall/November? 

The most important thing is that your follow up photo confirms that the plants are not Japanese knotweed. So yes, they are something in that bamboo genus/species, but I can’t pin it down because there’s always the possibility of a nursery cultivar. You should definitely talk to others, like county ag folks or the nursery association, and find out if it’s known to be in other places. It probably is, and then the question focuses on propagation.

It’s not unusual to hear about people excavating their bamboo or knotweed and then seeing it come back with a vengeance in 4-5 years. I’m intending to go to Ireland this fall to see how they manage their problem areas, and I know that their guidance is to remove all fill down to 9′ depth. That’s pretty crazy, but it’s what they do. Digging out “almost everything” is not enough to be a permanent eradication, but it’s progress. You need to keep at it.  No compassion or tears.

And as you monitor for a recovery, you need to aggressively install some strong native plants, especially south of the infestation. They need to steal away as much sunlight as possible, so big leafy plants like burdock are great.

Forget the hayfield idea until this is under control. The trick is getting the knotweed or bamboo cut while not cutting the native plantings. That’s probably hand work, and kind of tedious, but it’s not difficult. It’s what I do, and I have loads of fun.

Moving on, soil disturbance is best done when the ground is either frozen or dry or both. Be sure to clean machinery!

Wildlife using the space is a secondary consideration if this is a non-native species. With such an infestation, the “normal” world that all the local critters evolved for is turned upside down. So just focus on completing the eradication and the wildlife will adjust. I’d say right now the most important thing is to keep as much milkweed as possible to help the monarchs.

Since I don’t use chemicals, and I tend to avoid soil disturbance, my approach has usually been:

  1. Go on site in the fall and do a cut right after flowering. This intercepts all the sugar that would otherwise be getting stored in the roots. You may need to do two fall cuts, I’m not sure when the growing season tails off where you are located.
  2. Also clean up the site; get all the barbed wire out of the way, dead stalks, whatever, and install the first batch of desired plants for competition. They’ll need some follow-up watering.
  3. Focus on “securing the perimeters” of the infestation. Any rhizomal spreading plant species will respond to stress by going sideways. So put in tough competition around the edges, things like irises or hostas with dense root clumps. Even a strip of black plastic can help contain the expansion response. I don’t have the magic formula for that, it’s something to keep track of and learn as you go. Do not try smothering a patch like this without first doing a good job of securing the perimeter. I’ve seen few success stories with smothering.
  4. Now you’re all set to dive in when spring rolls around.
  5. Continue the cutting process, never letting the growth get above 10″ tall.
  6. Cuttings get tossed onto pallets on site, no removal necessary. Let them air dry/sun bake.
  7. Sure, if it’s easy to get one of those big root nodes unearthed, go for it, otherwise move on.
  8. When I cut, it’s absolutely flush to the ground. I use a scythe. If you leave a couple inches of stubs, those will harden off and be wicked sharp – dangerous enough to go through your foot or hand if you have an unplanned event.
  9. Keep at this aggressively for three full growing seasons, continuing to install more desired plants.
  10. By Year 4, you are well on your way to a transitioned site. Not yet done, but you’re over the worst of it as long as you don’t walk away.

Again, be sure to talk to other agricultural folks about this (such as your university extension service). Excavating really deep is not really the ideal approach, so it should be a last resort. If possible, goats may be incredibly effective with this plant. You’ll find that goats prefer the little juicy stems over the dried, hard canes. The goal with knotweed or bamboo is to never let the re-growth get tall enough to harden off the stem. I say 10″ for knotweed, that’s when it is drawing sun energy rather than root energy, and we want to starve the roots.

My knotweed approach hinges on the fact that the seed is essentially non-viable, but I don’t know if that’s true here. You should find that out, although in the end the control regimen doesn’t really change much. You’ll still want to focus on Transition of the landscape going hand-in-hand with the eradication work. We just want to make sure viable seeds aren’t coming in from elsewhere.

So with that said, this land seems relatively level. You should be able to go “fairly aggressive” with control and not cause erosion issues. I’ve been known to divide up my worksites based on topography. I might uproot /excavate in one area, but shift gears as I approach a slope or wetter ground. So there may be a need for a good blend of techniques here. That’s what notes are for. I’ve learned that knotweed grows insanely fast in May and June, but then things slow down. I learned that by documenting re-growth. Is that true in Arkansas? Maybe, don’t know…but knowing this helps with planning and efficient use of labor.

It’s pretty important with rhizomal populations to eradicate the entire patch at once. You can nibble in on the sides for a while, but to stop photosynthesis, you have to stop all above-ground growth. You should definitely set some benchmarks and photo-document the annual progress, complete with new species moving in.

Final thought – there may be some real use for the material. I’d avoid moving it off site, but if it’s air-dried, there could be some uses for good firm poles. Or make paper. It’d be a shame to burn all that debris, so if at all possible, the best approach would be just to air-dry it for several years and let it disintegrate someplace out of the way. Check in on occasion!

Note that it’s always difficult to diagnose a site or give advice without setting foot on the land. There is often confusion identifying species; photos are hugely important. Though I control knotweed, advice can be broad in relevance, and I always welcome critique or corrections or lessons-learned. The hope here is to help you, the landowner, come away with a kernel or two of truly useful information.

     Mike Bald, Founder of Got Weeds?, Vermont

ELA members have spent hundreds of hours learning the best ecological solutions to problems in the landscape. You can benefit from all that accumulated knowledge by posing a question to our experts. If you are stumped by a problem in your landscape or are looking for a second opinion on a potential solution, ask ELA’s Eco-Pros. Send your question to ela_new@verizon.net. And if you need additional help, refer to the listing of ELA Professionals.

***

Each author appearing herein retains original copyright. Right to reproduce or disseminate all material herein, including to Columbia University Library’s CAUSEWAY Project, is otherwise reserved by ELA. Please contact ELA for permission to reprint.

Mention of products is not intended to constitute endorsement. Opinions expressed in this newsletter article do not necessarily represent those of ELA’s directors, staff, or members.