Garden Sunlight: Auditing Your Space

Hours of sun per location.
Beds coded by sunlight.

The main driver of gardening success seems to be sunlight and matching plants to the place in your garden where they can thrive by getting enough rays each day. One way to analyze your space is to watch where the snow melts first — these are likely your “hot spots.” You could spend a midsummer day with a clip board and pencil to mark when the sun hits and leaves certain beds. Alternatively, you can use your fist, as I did.

(image source)

This weekend, I made a sun map of the institute grounds. I did this by walking a grid in the yard, represented by the numbers in the first figure. I had gone to a solar angle calculator and found that in the summer, the sun is about 70° over the horizon. Also, I knew that by extending my arm at about that angle towards the south, turning my hand and looking at the width of four fingers superimposed on the sky, I can estimate how much of the gap between trees represents an hour of the sun’s passage. In about twenty minutes this weekend, I made a quick plot.

I then used contour lines to differentiate between full-sun, partial-sun/shade, and full-shade areas in the garden. I won’t go into how to draw these lines (see a rough video here), but everything shaded red “above” a red line is full sun, meaning at least six and preferably eight hours of sun each day. The yellow-shaded areas above the yellow lines are partial sun or shade (which are the same thing in nursery-speak) and have three to six hours of sun per day. Full shade, represented in white, is anything under three hours of sun.

This map was about what I expected after growing here for two years, but a few areas had less sun than I expected. This will help me plant this year, though, as I now know what beds are full, partial, or no sun. I converted my bed map to reflect these data, shown in the second map figure.

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