I've been trying too create a sugar cane farm that uses pistons activated by a button to cut the sugar cane off on the second level. I've noticed though that instead of cutting the sugar cane, when the piston extends the top levels of the sugar cane simply disappear / de-spawn. I've followed the you tube videos and cant for the life of me figure it out.
Is there a bug right now preventing this from working?
They seem to work best for me with a piston at the middle of the plant and one for the top of the plant. You'll want both to fire at the same time and the water stream they fall into should be two wide. There is also a dropped item limit so you don't want too many harvested at one time, if you have a big farm its best to stagger the harvesting.