Sun Study: Part 1

One of my 2021 gardening goals was to do a formal sun study to map out what parts of the yard get the most sunlight. Our yard is challenged by a number of trees, including a large oak and a black walnut tree. While most of the garden gets at least some sunlight, I couldn’t tell you off-hand what parts of the yard will be in sunlight and what times of the day.

For this sun study, I decided to observe the yard every hour on the hour throughout the course of the day to see when different parts of the garden were in full sun versus full shade. The thought of doing the entire yard at the same time was a little overwhelming, so I’m breaking the yard up into zones.

Here’s my rough sketch of the house and yard (not to scale):

East is the top of the image. West is at the bottom.

The house is the white area. The green is the raised vegetable plot beds. The purple area is what I call “the orchard.” This is where most of the plum, pear, and apple trees live. The red area is a trellised slope on the southwest side of the house with raspberry bushes and grape vines. The blue is the rest of the backyard – mostly lawn and small beds next to the house. The yellow is the front yard.

I started with the vegetable garden zone. I tracked sun and shade on July 2. Unfortunately, the day started out cloudy, so I don’t have much data between 7 and 10 am. What I know is that the sun rises around 5:30 at this time of the year, and it peeks over the house and into the backyard at around 7am.

7 AM

By 10 AM, the sun is shining over the house but the oak tree shades the raised beds from much of the sun’s rays.

10 AM

By noon, the westernmost four raised beds are getting some sunlight, but the rest of the beds are still shaded by the oak tree.

12 PM

The next hour, at 1 PM, two more raised beds, including my new cinderblock bed are in sunlight. The squash are still in shade.

1 PM

By 2pm, all of the easternmost raised beds are in full sun, but the black walnut tree has already started shading the most southwest raised bed.

2 PM
2 PM

As the sun continues it’s journey behind the black walnut tree, my cinderblock garden is again in shade by 4pm.

4 PM

How disheartening? That’s barely 4 hours of full sunlight! At the peak of summer! I suspected the garden space wasn’t getting quite as much sun as it needed, but I was hoping it was closer to 6 hours than 3 hours. The beds on the north side get a bit more sun, but not much more. This is probably the explanation as to why the squash are so small and the beans aren’t producing any flowers yet.

I’ve read that a vegetable bed needs at least six hours of sunlight a day, and in our northern latitude, where the sun’s rays are less intense, eight hours of direct sunlight would be preferred. Ha! My plants are getting half that.

In a perfect world, we would chop down that darn juglone-producing, sunlight-thwarting black walnut! But it’s a beautiful and healthy tree that provides privacy between us and the school next door. Plus, it’s not on our property, so even if we wanted to chop it down, we couldn’t. Bummer. I’ll have to continue the sun study in the other four zones of the yard to see if any parts of our yard get a full six-eight hours of sun. I’m not optimistic

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