Tree

os.loadAPI("moveAPI")

function tree()
  moveAPI.move("f dd")
  turtle.placeDown()
  while turtle.detectUp() do
    moveAPI.move("u")
  end
  while not turtle.detectDown() do
    moveAPI.move("d")
  end
end

function row()
  for i = 1, 4 do
    if turtle.detect() then
      tree()
    else
      turtle.forward()
    end
    if i ~= 4 then
      moveAPI.move("f f f")
   end
  end
  moveAPI.move("f")
end

function main()
  moveAPI.move("u u u r f f f f f f l f f f")
  turtle.turnLeft()
  row()
  moveAPI.move("r f f f")
  turtle.turnRight()
  row()
  moveAPI.move("l f f f")
  turtle.turnLeft()
  row()
  turtle.turnLeft()
  moveAPI.repeatMoves("f", 12)
  moveAPI.move("l f f f f f f d d d")
  turtle.turnLeft()
  for i = 2, 16 do
    turtle.select(i)
    turtle.dropDown()
  end
  turtle.select(1)
end

turtle.select(1)
itemDetail = turtle.getItemDetail()
if itemDetail ~= nil and itemDetail.count >= 12 and itemDetail.name == "minecraft:sapling" then
  main()
else
  error("put at least 12 saplings in slot 1")
end