Bad rhizome day

Yesterday I rhizome pruned a couple of my in-ground Phyllostachys bamboos, and ended that post with a comment about having at least 6 more to do. I decided to tackle a couple of more today. The first one went fine, and I didn't find any escaped rhizomes. That could be because it's the bamboo that escaped last year and put up some shoots in my lawn this year (which I recently dug out and potted up). So I've been keeping a closer eye on that plant.

With the second plant I didn't get so lucky.

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Here's today's problem plant:

It's Phyllostachys aureosulcata, or "Yellow Groove" bamboo, the most common bamboo grown in the St. Louis area. As you can see it's grown in a raised bed:

Since it's built on a slope, the one side of the bed is deeper than the other. In this photo the left side is the deep side. I found a few rhizomes coming out from under the wall on this deep end earlier this year, and I thought I got them all.

Apparently I missed one. From what I can tell, it came out of the box about 12-18" from the end (on the left), then grew parallel to the box edge, spreading to the right (the shallow end). That's where I found it. Since it was parallel to the box edge, my previous pruning efforts missed it completely.

The ground is pretty dry and was coming up in clumps as I dug around the edge, so the rhizomes were easily discovered and pulled up. Here's the soil right now:

(Not very nice for planting anything.) I say rhizomes (plural) because the one main rhizome that escaped branched out into 5 (five!) separate rhizomes.

The total length from end to tip was about 8'. If I hadn't found these today, they would have put on several more feet before they stopped growing, and I would have had shoots coming up all over the place next spring!

So apparently the rhizome went almost straight down under the edge of the box, then came back up to be an inch or two below the surface -- something like this:

You can see that it actually must have been at the surface at one time, because it turned green (sunlight exposure activated the chlorophyll) at one point:

Too bad I didn't notice it then, as it would have only been 3 feet long and easy to pull out -- although not nearly as impressive as it is right now:

As I went around the deep end of the box again, I found another rhizome just starting to poke out:

I guess I'm going to have to keep a close eye on this end of the box. No signs of trouble in the shallow end, which is a little scary. Are the rhizomes just going a lot deeper at that end? I guess I'll find out in the spring.

The branching of this single escaped rhizome hopefully points out how important it is to control every rhizome:

Even letting this one escape into my yard resulted in 5 separate rhizomes. Next year each of these 5 would produce several of their own rhizomes, so you can see how quickly I'd have a big bamboo problem.

If you think about it though, I'm getting better. Last year I missed a couple of rhizomes completely, leading to shoots in an unwanted place this spring. This spring I missed just one rhizome, and discovered it just a few months later, well before it had a chance to become established. Extrapolating on this, I guess I won't be missing any more rhizomes at all this time (and from now on), right?

If only it worked that way.

I'll guess I'll just need to remain diligent in my pruning.