It works, but the trench needs to be renewed each year. I find mounding the center a couple of feet also helps. Growing bamboo near trees also lessens the spreading. Shade tolerance varies and you want to find a happy medium.

I've never used the technique but since many bamboo species have roots that go down 2 to 2 1/2 ft, wonder if a 1 ft trench works on all baboo? Rgds

I agree with fredgpops. I think that a 2' trench or barrier is the minimum. A 1' deep trench will probably catch the majority of the rhizomes, but not all, and you want a margin of safety.