I gave a talk at TechLiminal recently. The topic was Urban Farming 101. I think I overtalked…in fact, I know I did. Turns out there is quite a bit of ground to cover (haha) when it comes to growing and raising your own food. Luckily with this blog, I can keep on talking.

I created this blog to share both the experience of urban farming as it unfolds and the how-to’s. With that, lets talk about light and shade. First, let me introduce my friend the protractor (apparently this image is printable and usable):

I attended a home growing class a few years ago where the instructor distributed nifty “maps” of the sun’s path throughout the year in the Bay Area (click here to download a pdf of the map on google docs) and taught us to use this map of the sun and a protractor to determine how many hours of sun a given spot in your yard will receive throughout the year. This will help you decide what may grow well in certain locations of your yard.

Do this by taking your map and protractor to the desired location and while holding the protactor flat with the arch outward and straight side facing you, point the ninety degree mark on the protractor exactly due south. Now look at your “horizon” which will be where the open sky meets an obstacle in your yard. You are going to use the protractor to plot degrees on the vertical (y) and horizontal (x) axis. For each visible obstacle starting on your left, note the degrees from ninety it first starts. That will be the degrees on the x axis. For the first time it appears in your horizon, consider the angle of it is located from the flat surface of the protractor. You can likely estimate this if you know basic angles. This will be your y axis. Now plot the point on the appropriate location on your chart. As you move from left to right, plot only the transitions in height in your horizon. Once you are done with the full 180 view from where you are squatting (don’t worry about the north side. The sun travels from east, south, west), connect the dots and shade beneath the resulting line. The unshaded portion of your plotted horizon will indicate the hours of light in the day for a given month of the year.

If you have a deciduous tree which is bare part of the year, when you shade make only sparse lines through that area on the map to indicate partial shading. There were some brainiacs at the talk that could recalibrate the Bay Area map to accommodate any longitude and latitude, unfortunately unless they comment to explain how, I am at a loss. The same people explained how they could plot the points by using a photo of the yard…but sitting at your computer to garden sort of defeats the point, smarty pants.