Mud bamboo farm

A per column bamboo farm by LaZ1en Farms. Each plant sits on its own mud block with an observer watching it and a piston beside it, so the moment the bamboo grows the piston snaps it off and a hopper underneath pulls it into a shared chest. Mud is the one block that matters: it is fractionally shorter than a full cube, so the hopper can reach the item through it. The design tiles sideways, one plant at a time, and you build it as wide as you want bamboo.

The redstone shown in the video does not work for a lot of builders. Put the dust behind the observers rather than behind the pistons. Rosie_Meg gives this fix to four separate people, thoricmanx1506 and Astrozeo confirm it, and aguy-x4l runs dust on both blocks.
It has to be mud. Dirt and sand fail because they are full blocks and the hopper cannot pull the bamboo through them. lukejbonner spells out why, and LaZ1en confirms it in the replies.
Drop the hopper per plant and run one hopper minecart on a rail underneath instead. Much cheaper in iron, and damp_tostr3282 points out a minecart pulls through dirt as well, so the mud stops being necessary at all.
rixei7756 skips hoppers entirely and lets a water stream carry the bamboo to one end. driverdoraemonviesky288 warns it leaks, bamboo fired by the piston sometimes misses the water.
joshp6061 and WorldofSteel.l cut the observer count by raising the redstone a block and running one observer per three plants. ArlosPA disagrees, in this layout each observer only triggers the piston directly beneath it, so all of them are needed.
Height does not matter, you just have to be within 128 blocks of the farm for it to tick.