Simple bone meal tree farm

A single sapling oak farm by BasicRedstone, eleven items and about a minute to build. One dispenser bone meals an oak sapling into a tree and a column of pistons snaps the trunk into a hopper and chest. There is no rate anywhere and no automation beyond the lever, so what it really is is a bone meal to wood converter that fits in a corner. The top comment on the video is a builder finishing it and realising they now need a bone meal farm.

• Use 7 pistons rather than 5 so the leaves get pushed clear and the next tree can grow, and put a block 7 or 8 above the sapling so a large oak never forms and jams the whole thing. This is the most upvoted improvement on the video.
• The dispenser stopping after a few ticks is the most reported fault. Several builders find the hopper orientation locks and never feeds it, and the working answer is a redstone clock driving a dropper instead.
• If the bottom piston will not fire, add another redstone torch facing the back of the block above the comparator.
• It is oak only. One builder fed a long run of bone meal into a birch sapling and got nothing out of it.
• Leaves are disputed. Two commenters say trees grow through leaves fine and that the real jam is the large oak, not the foliage, which is what the block above prevents.
• On Bedrock the lever has to become a clock and the torches come out, and even then the first piston does not fire, so the first log gets mined by hand each cycle.