When we trench for bamboo, we have to put in a rubber or thick plastic wall. 3ft down as I remember... What are you going to do for a barrier in the trench?
My two acres has three sides of bamboo, each leg about 320 ft, about 3 to 5 ft thick, and about 30 ft tall. Anybody need some fishing poles, or you can make flutes or wind chimes out of them. Maybe even a bamboo doorway.
You must not be on good terms with your neighbor. There is a patch near me that has spread over a half acre. Another neighbor had to get a back hoe to remove what was growing in his yard and some still came back the next growing season. Good luck with trying to contain it.
Was mowing it down as it spread not an option? I planted 2 plants about 4 years ago to create a screen around a deck, it has spread all through the bed as I designed it to, as the runners come out i just mow them down and they dont seem to come back. Bamboo is a grass after all.
It seems that trench would be a maintenace issue over time and even a possible safety hazzard.
looks like fun work though