Spruce

function checkFuelLevel()
    if turtle.getFuelLevel() == 0 then
        turtle.select(16)
        turtle.refuel()
    end
end

function placeSapling()
    turtle.select(1)
    checkFuelLevel()
    turtle.select(1)
    turtle.forward()
    turtle.turnLeft()
    turtle.place()
    turtle.turnRight()
    checkFuelLevel()
    turtle.select(1)
    turtle.forward()
    turtle.turnLeft()
    turtle.place()
    turtle.turnRight()
    checkFuelLevel()
    turtle.select(1)
    turtle.back()
    turtle.place()
    checkFuelLevel()
    turtle.select(1)
    turtle.back()
    turtle.place()
    for i=1, 7 ,1 do
        checkFuelLevel()
        turtle.back()
    end
end

function chopUp()
    turtle.select(15)
    while turtle.detectUp() do
        turtle.digUp()
        checkFuelLevel()
        turtle.select(15)
        turtle.up()
    end
end

function chopDown()
    turtle.select(14)
    while turtle.compareDown() == false do
        turtle.digDown()
        checkFuelLevel()
        turtle.select(14)
        turtle.down()
    end
end

function checkGrowth()
    for i=1, 7 ,1 do
        checkFuelLevel()
        if turtle.forward() == false then
            turtle.dig()
            turtle.forward()
        end
        turtle.select(15)
        if turtle.compare() then
            return true
        end
    end

    for i=1, 7 ,1 do
        checkFuelLevel()
        turtle.back()
    end
    sleep(30)
end



--main
placeSapling()
while true do
    turtle.select(15)
    if checkGrowth() then
        turtle.dig()
        checkFuelLevel()
        turtle.forward()
        chopUp()
        checkFuelLevel()
        if turtle.forward() == false then
            turtle.dig()
            turtle.forward()
        end
        chopDown()
        turtle.turnLeft()
        turtle.dig()
        checkFuelLevel()
        turtle.forward()
        turtle.turnLeft()
        chopUp()
        checkFuelLevel()
        if turtle.forward() == false then
            turtle.dig()
            turtle.forward()
        end
        chopDown()
        turtle.turnLeft()
        turtle.forward()
        turtle.turnLeft()
        turtle.back()
        placeSapling()
    end

end