Pythagoras and Potatoes

Published on 04/21/2009

This past weekend I got my first veggies in the ground! On Friday night I cut my seed potatoes and set them out with a fan on them so the cut edges could scab over before I put them in the ground. Then I grabbed some graph paper and started to figure out my layout. I am basing my plant spacing off of the suggestions in The Sustainable Vegetable Garden, and it recommends what it refers to as offset or hexagonal spacing. Basically, draw a grid of hexagons and put a plant at each vertex and in the center of each. This spacing technique is designed to allow more plants per square foot over the traditional row spacing as well as other benefits related to the fact that the leaves from the plants are closer to each other forming a canopy of sorts that serves as a natural mulch to keep moisture in and weeds out. It took me a little while to figure out practically what that would look like--I had to pull out some algebra and trig. I used the Pythagorean Theorem to figure out what the distance would be from the center of the hexagon to each edge. I figured out that this distance (X) can be calculated as follows, where L is the distance from the center of the hexagon to any of its vertices (which is the spacing given by the book, 9 inches for potatoes):

X = squareRoot(3/4) * L

So, effectively you have rows of potatoes where each potato is 9 inches apart, where every other row is shifted by 4 1/2 inches, and the rows themselves are about 7 3/4 apart, as given by that formula (well, 7.794... technically). Who wouldda thought planting potatoes would involve so much math! It was fun figuring it out.

Anyway, so I drew out the layout to scale and figured out that I could get 32 seed potato pieces in the four by six foot bed, and that worked out great because I had 34 available. While I was doing that my dad was trying to figure out some technical stuff of his own for a job he was doing on Saturday. When both of us finished our thinking and drawing I showed my dad the layout and we talked about how to actually implement it in the bed. He suggested putting marks on the long sides of the beds where each row would go (7 3/4 inches apart) and then putting marks 4 1/2 inches apart on a board that I could slide across to line up with each row mark. That's what I ended up doing and it worked wonderfully. I tied a piece of potato on a length of twine to use as a plumb bob and used that and the marked board to place each potato where it was supposed to go. I'm sure you all think I'm crazy being so exact on this, but that's just how I think, and it's easier for me if I can do it by some formula rather than just guessing.

So, on Saturday I got out the shovel and the level and set the beginnings of the raised bed to where it was more or less level. Then I added a two by four on top all the way around to make it about thirteen inches high all together. Then I mixed some of my clay soil with a lot of the composted horse manure that I got from our family friends Randy and Kathy Arn a couple of weeks ago and filled the bed to about four inches deep or so. That was all I had time for that day, and I wanted to give the potatoes one more day to scab over, so I actually did the planting on Sunday. After putting the potatoes where they were supposed to go and taking some pictures, I covered them with four to six inches or so of the same clay soil and composted horse manure mixture I put in the day before. It was a pretty fun experience and the weather was great for it. Next up, hopefully onions and carrots!