The plants themselves don't drop anything. Only if the plant matures
can you dig potatoes from the soil. If you can reach the soil from the
side you can save yourself one dig by digging the soil as that will
remove the plant from the top, but otherwise you need to dig twice:
once to remove the plant, once to dig out the potatoes.
You get 3-5 potatoes. Each potato gives one (set of) "potato eyes"
which are the clones that can grow back to potatoes.
The plant itself is purposedly drawn "low" and not as a full block as
that's how the plant grows without support, mostly close to the ground.
Be careful not to dig the plant when there's flowers! You have to
wait until the soil below shows potatoes. It's fairly easy to see
the difference, though.
