could use a sawzall with a fine tooth wood blade. how big of culms are you talking about?

Use a hacksaw

I second the sawzall suggestion if you already have one. It makes a very smooth cut with no effort and in no time at all. And it gets into tight positions where a hand saw is too cumbersome.

A sharp pair of branch loppers works well for pretty good size culms. I've also used a fine tooth Japanese saw a few times, but bamboo culms have enough silica in them that I don't use it frequently because I worry about dulling the teeth. You can get a long, fairly tough, medium tooth Sawzall blade for about $4. I've also used a small bow saw with large teeth, and it works pretty well, but its size makes maneuvering inbetween close culms difficult. If you're just talking about cutting culms off at ground level, the fineness of the teeth is not a big deal. You can always clean up any messy residual fibers with your pruning shears.

Battery-powered recipricating saw with a long, metal-cutting blade, which provides the hardness (vs. a mild steel wood blade) and the fine teeth, something like 20+ TPI.

Corona RS-7265 or RS-7041 . The smaller 7041 is good for the 3/4 in. and larger up to 3 in. boos and the bigger 7265 is well really huge so say anything from about 2in. heavy wall or 4in. thin wall up to about 6in. boo.

Some great, innovative suggestions. Don't have a sawsall, but could buy a sawsall blade and use it with gloves on. Since I already have a hacksaw with a blade, I'll try using the blade without the hacksaw in February, when I thin out my culms. Of course by that time, I may decide to splurge on the $40 Japanese bamboo saw. Thanks for the input ...

always nice to own a sawzall you would be amazed at how mych you use it. I keep all my old blades for cutting out tree and hedge stups and roots works wonders.

Seattleboo-
A hacksaw blade should work fine. Invest in one of those handles that you can get for about $2 that a hacksaw blade slides into. It's just a flat handgrip and the hacksaw blade slides inside it and projects out the front. Very handy for tight quarters...

For $40 and perhaps just a bit more, get an electric reciprocating saw. It's a tool that all house owners should have any way.

Someone suggested using an angle grinder with a metal cutting blade, I've used it for clums up to 2" and it works great Cuts them even with the ground.

I've used a 4" angle grinder with a metal cutting abrasive DISC (not blade). Cuts very clean, the abrasive heat also seems to anneal the cut, fwiw.

Also a very neat way to trim branches closely from a bamboo pole, since if you did't cut the branch as close as you want, you can use the disc to grind the branch stub down to be flush.

You can pick up handsaws with japanese tooth designs for under $20 online. Try lee valley, but there are many others.