Knowing the daily and annual sun positions helps to make landscape designs accurate and realistic. Sizes of extremely shady or sunny spots are easy to estimate.
Let us look at daily and yearly sun positions for my northern hemisphere yard.
Scientists use formulas to compute seasonal variations. However, web sites similar to theThe Old Farmer's Almanac make available interactive tools that establish sunrise, sunset and hours of daylight for U.S. and Canadian locations.
For example: On March 15, 2006, the sun rose over my yard at 6:02am; it set at 5:57pm, and there were 11 hours and 55 minutes of daylight. A week later on March 22, 2006, it rose at 5:50am, set at 6:05pm, and there were 12 hours and 15 minutes of daylight. Yes, days genuinely get longer around the vernal equinox.
Three numbers are necessary to determine the sun's yearly and daily positions in the sky:
- First is latitude. Access a site like TopoZone to find this. My home's latitude is approximately 42.5° north.
- Second is 23.5° - the tilt of the earth toward (summer solstice) or away from (winter solstice) the sun.
- Third is 90° - the position when the earth seems not tilted toward or away from the sun (equinoxes).
Using these numbers, I can estimate the sun's yearly positions due south over my yard. The sun's height at the equinoxes is 47.5° above the horizon (90° - 42.5° = 47.5°). Over my yard, height at summer solstice is 71° above the horizon (47.5° + 23.5°=71°); height at winter solstice is 24° above the horizon (47.5° - 23.5° =24°).
Knowing this, I can plan appropriate designs for sunny and shady locations. It will be easy to establish how large or small these areas will be as the year progresses. For example: I can begin to visualize a design and what activities and plants are appropriate for the north side of a house that has a huge deciduous tree planted to the west of it.
Plants like ferns and hosta are good choices. They die back during the winter but thrive in slight summer shade. Light filtering through the tree's leaves on to some wicker furniture makes an inviting relaxation spot.
Spring and fall-blooming (solstice) bulbs might grow well along this side of the house and under the tree if the soil is not too dry or moist. However, winter shadows and shade will be long and deep here. Birds can add winter color and movement by coming to feeders on the tree or under the eaves. Tree branches make perfect resting spots for them.
©
Text and photograph by Georgene A. Bramlage, [March, 2006]]. Reproduction without permission prohibited.
