Although it is common biological fact that plants need sun for photosynthesis, the University of Illinois Extension explains, "Different plants need different amounts of sunlight to produce a sufficient amount of food to grow and maintain health and vigor." Planting instructions usually include a recommendation for the lighting conditions for planting each crop where it will best thrive. If you want to plant seeds or seedlings that call for "full sun," knowing what that means will help you select the optimal planting location.
According to Penn State Extension, planting in full sun requires a site that receives at least six hours of direct sunlight every day. This seems straightforward, but light and shade change as the sun moves through the sky during the day and in different seasons. To accommodate these changes, choose your planting site in relation to planting time and the daily pattern of light and shade. The six hours do not have to be continuous, advises the UI Extension. As long as the direct, unfiltered sunlight time meets or exceeds the minimum, your light-loving crops will get what they need to thrive.
Gauging the amount of light in a planting location can be a subjective perception. For a more objective measurement of full sun, you can use a light meter to calculate a more precise reading of the light conditions in your garden measured in foot-candles. A clear, sunny day may measure 10,000 f.c., according to the University of Arizona College of Agriculture and Life Sciences. Check with your local nursery or garden center to purchase a light meter and place it in the planting area. Take several readings throughout the daylight hours to calculate an average and determine whether the area gets enough direct light to be considered full sun.
The Sunniest Spots
A planting area with southern exposure generally receives the most sun over the course of a full day, explains the Cornell University Department of Horticulture. Western exposure is your next best choice for full sun because the garden will receive the full benefit of afternoon sun to make up the six hours of required sunlight for sun-loving plants.
Crops for "Full Sun"
Once you've identified the best planting area for full sun, matching it with the right flower or vegetable crops will kick-start the energy-producing process of photosynthesis and let your sun lovers thrive. Sun-seeking vegetables include tomatoes, cucumbers, peas, beans, squash and corn. Landscape plants that require full sun are numerous but include some varieties of cotoneaster, hydrangea, ivy, rose, sumac, pine, alder, cedar, maple, spruce and thyme. To identify specific sunlight requirements, read the planting instructions that came with your seeds or starter plants or seek advice from your local nursery to help you pair each of your desired crops with the right light conditions for best growth.