How to Estimate Sun Hours for a Garden Bed
Select useful dates, place the receiving point correctly, model seasonal obstructions, and interpret direct-sun hours for a garden.
Last reviewed August 8, 2026A garden can contain full-sun and shade conditions only a few metres apart. Estimate each important bed at its own point and compare the dates that cover the real growing season.
Pin the bed, not the address
Place the receiving point inside the planting area. Street-address coordinates or the center of a large yard can miss the shadow edge that matters for a bed beside a wall or tree.
Model the seasonal skyline
Add the nearest buildings, solid walls, and mature trees first. Compare tree opacity and crown width for leafy and sparse periods. Fences with gaps, pergolas, and sloped terrain require simplified scenarios rather than a single exact obstacle.
Match dates to the crop calendar
Test the beginning, middle, and end of the growing period. A midsummer total can overstate exposure for spring or autumn crops. Use the same sample dates when comparing candidate beds.
Interpret hours as a screening metric
Plant labels often group exposure into broad bands, but species, climate, heat, reflected light, and irrigation still matter. Use direct-sun hours to compare locations and identify field observations, not as a guarantee of plant performance.
Questions about this method
Does dappled tree light count as direct sun?
SunCarta uses an opacity-based approximation for a tree crown. Real dappled light varies continuously, so compare multiple opacity scenarios and observe the bed when possible.
Should I use one point for a long garden bed?
No when a shadow boundary crosses it. Test the ends and center separately to see whether the bed contains materially different exposure zones.