When it comes to the question of how to most efficiently mow
the lawn, arguments inevitably come down to two main approaches: You either mow
in rows, or spirals. With the help of a famous puzzle maker, a few lawn-mowing
experts and some simple mathematical calculations, we answer the question once
and for all, which one is the better technique?
The first factor to consider is distance, and this one is
easily ruled out by the first law of mowing a lawn: Don't go over the same
patch twice. This given knocks out many well-meaning, but clearly inefficient
routes on an unimpeded patch of lawn. (Note: For argument's sake, we compared
techniques on an empty square plot—fancy garden mazes, orchards or sheds are
surely part of the picture for most mowing, but in order to answer such a
broad, important question as rows or spirals, we must make like the great
philosophers and lay our argument down on a theoretically perfect plane.) Few of the best riding lawnmowers can help you in the best way.
Now that we're down to a fixed square footage—and
distance—of lawn to mow, we can focus on turns. If you have a push or zero-turn
mower, you can skip straight to the next paragraph, but if you're using a
riding mower, stick with us here and tackle the problem of turning distance. If
you look at your every day, run-of-the-mill John Deere riding mower, you have
anywhere from 15 to 22 inches of travel before you can make a 180-degree turn.
Assuming the same number of turns, the way that this play will affect the
outcome of your efficiency will depend on how tight your turns need to be. If
your turn is as tight as the tractor is long, minus 15 to 22 inches, you're
going to be left with patches—uncut grass that will force you to break the
first rule of lawn mowing. In the battle between spirals and rows, this is only
a hindrance for a spiral that is not perfectly plotted. For the careful mower,
then, rows and spirals remain tied so far on any type of mower.
Now, onto the big question: Which technique requires more
turns? As it turns out, neither. The following illustrations by master puzzler
Scott Kim shows that on a square 16-foot by 16-foot lawn, both the spiral and
row techniques take a total of 30 turns; 14 left and 16 right for the rows, and
30 right turns for the spiral. One could argue that to mow in rows, there are
half as many turns—when you get to the end of a row you make two 90-degree
turns, which you could also count as a single 180-degree turn. Still, the total
number of angular degrees you turn is in either case the same.
