Here's a Yellow Groove culm that has some weird damage. A couple of the culms had this on the lower few feet, but then the rest of the culm looks completely normal. The other side of this culm is "smooth" -- no crack in it. Just looks like a bunch of compressed nodes from that side. The culm is about 1" in diameter or so.

(sorry for the blurry photo)

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Alan.
My blog: It's not work, it's gardening!

I'd guess that a slug or other critter nibbled a spot while the shoot was 'telescoped in' and the mark then elongated with the shoot.

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Brad Salmon, zone 5b/6 Southern Indiana
Winters -20 to -25C. Summers 30 to 35C , humid. 115 cm annual precipitation, frost free from May through early October. 259.3 meters elevation. Growing 150+ species. http://www.needmorebamboo.com/

So if they didn't bite deep enough, that would explain why the higher portions of the culm weren't affected.

Does it also explain why the nodes are compressed?

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Alan.
My blog: It's not work, it's gardening!

A mutant gene. Like when Bluebonnets have triple stems? Unfortunately not a reproducible trait I suspect.
MarCat

I've seen on a french forum something very similar to this. It's almost like there are conjoined twins with a shoot and looks pretty cool. Does your culm split into 2 separate culms at the top?

I found it on this thread.
http://lesbambous.fr/forum/viewtopic.ph ... 01&start=0

Here's the pictures.

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http://www.flickr.com/photos/31489820@N02/

http://stevespeonygarden.blogspot.com/

That's cool, but mine is a single culm at the top. There are 2 different culms that have this damage or form, and they were a foot apart or so.

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Alan.
My blog: It's not work, it's gardening!

I found a double stemmed dandelion before. it was awesome until the lawnmower ate it.

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http://bensbamboo.blogspot.com/