Getting Rid of Invasive Species of Plants: False Bamboo in Ontario (Japanese Knotweed, Chinese Bamboo)

The old house I inherited, has a patch of ground where False Bamboo or Japanese Knotweed has taken over. I thought if I simply cut it down it would die off. Well it is pretty luxuriant if the picture is any indication. You would think I have a very green thumb...but actually I have been trying to kill off the darn plant and it comes back more beautiful than before!

I have been hacking the stems down like a native in the Amazon, except I don't have a machete and these plants are growing in Northern Ontario!

I have been researching on what this plant is and how to contain it and am amazed to find that there are persons that love this plant even though it is very invasive and kills all other vegetation that attempts to grow underneath it.

The International Union for Conservation of Nature classifies it on it's list of the 100 most dangerous invasive species in the world. It originates from Japan where it isn't quite as invasive as in North America. In North America it has no native natural enemies to keep it in check. The plant limits diversity of vegetation where it grows by releasing chemicals that inhibit other plants growing in it's location. I can testify to that. Cut back that thicket and the ground is devoid of other plants; it is completely barren.

The plant grows very tall, over five feet and so dense you cannot walk through the patch. The stalks are semi-woody and hollow. The stems are easily cut with garden shears and there is no undergrowth to speak of, once cleared you are left with sharp hollow spikes and barren ground.

Luckily, the area is contained at this point, but eradication seems to be quite the problem. Cutting it down seems to grow a particularly verdant new crop, but I noticed cutting does allow other species to gain a foothold back into their own territory, since once cut back other species will once again have sunlight to grow!

The first year, I just cut down the plants and left them in a pile. Next year the new crop was just invigorated, as if I had done nothing. The second year I piled the cuttings and placed a tarpaulin on the green foliage and seem to have successfully rotted those stems and only a few shoots came up in the area that was under the tarp.

This year (the third) I redid the cutting earlier than before (no flowers and placed the green shoots under a tarp once again to rot the stalks and meticulously went through the area to cut each plant. Cutting each and every stalk is simple since the plant is easily distinguished from it's surroundings. Hopefully next season I will have cleared another area for other new plants.

Not entirely sure if I can eradicate this plant from the garden. A word of caution for would be gardeners: research this plant, do not plant unless you know you can contain it!

Cutting down the False Bamboo was relatively easy. Nothing but a pair of garden shears and some effort. It took a morning of work and the new growth was a pile of greens. I left the cuttings were it grew to discourage it going rogue outside it's boundary. Note there were no other plants under the canopy and the cuttings left awkward hollow stems sticking out that will dry and not be great to walk on.

 After the False Bamboo is cut down it should be rotted on site of the growing area and not allowed to re establish itself. Providing a tarp that does not allow light through will accumulate heat and destroy the growth under it.

Now we wait...will it grow back? Probably, but hopefully weaker by next summer! This will be repeated until I claim this area back from these tough and resilient  plants. 

Two months later, 

the False Bamboo has taken cutting in stride and is attempting a comeback. Though not as tall, and certainly not coming back in the area covered by the tarp, it has started new shoots from existing stalks and some frail new shoots from the roots.

Plan B 

Seeing as the existing root stalk is allowing new growth that seems more robust and the good fortune of rain to soften the earth, I decide a more efficient way of eradication might be pulling the new stalks instead of cutting them. Fortunately, the rain has softened the soil and quite a bit of root comes up with the stalk.

The area that was tarp covered from the previous year was uncovered when this year's first growth was cut down. The good news was that the growth in that area was weaker than on the area just cut down and left uncovered. What was heartening was the fact other plantsare starting to make inroads and reclaiming their own natural habitat. There is hope!

According to the video below, it will take ten years of diligent work to eradicate it. Oh bother!

It is a later spring than usual up in Northern Ontario. It is mid May and much of the landscape is still brown. I checked the false bamboo for signs of life and I almost missed them...

In among the dried stalks were "wine" red shoots, about two inches tall making their debut on the fringes of the tarp. At this moment, there does not seem to be any life in the old uncovered pile of false bamboo that had been allowed to dry and rot under the tarp for a season, but it did have some shoots last season which I pulled. It is too early to know if I will remove the turquoise tarp from last year's crop of false bamboo that I kept covered to dry , rot and keep in the dark. I think I will watch the old pile for awhile and buy some more tarps for the fringe areas.

So far the most effective treatment seems to be cutting the stalks and leaving them right where I cut them and covering them. Denying the plants light and not allowing the new growth of false bamboo an opportunity to strengthen the root system allows other plants to begin to re-establish themselves.

This spring, I seem to have made some progress. However, the battle has not been won and I need to be very vigilant for as long as it takes to eradicate this invasive plant...it is extremely hardy and resillient. Fortunately, the area can remain fallow for quite some time since this isn't normally a garden area. The tarps are unsightly, but necessary!

Summer 2011.... The new growth around the fringes is still very lush with Japanese Knotweed. The battle continues! The good news is that other new vegetation is starting to reclaim some of the area back. The tarp covered area from last year is fairly dormant with dead vegetation except for some anemic stalks of Japanese Knotweed snaking under the tarp towards the edges. The tarp has now been moved to cover another area widening the area reclaimed.

September 2011...The battle isn't over...I have cut this year's crop on the fringes three times. The last growth was smaller but I have no illusions if I left the patch on it's own it would reclaim it's area in no time. I am becoming slowly aware that covering the area permanently with a waterproof and lightproof tarp for a number of years may be the only choice barring using insecticide which I am loathe to use.

As you can see...this is a plant to avoid ever getting into your garden!