Look at any plant information tag and you will find icons telling you how much sun is required for the tree to thrive. Usually, the icons designate “Full Sun”. “Part Sun” “Part Shade” or “Shade”—but what does that really mean? Here are some general rules of thumb to help you understand the icons.
Full sun means 6 or more hours of direct sun. Usually this describes a south or southwesterly site with little to no shade at any time of the day from either trees or a structure.
Part sun means four to six hours of direct sun per day. Not all those hours need to be accrued consecutively—it could mean a few hours of morning sun plus a few more in the afternoon. When a plant prefers part sun, although it does not need to be in direct sun all day, it will grow and bloom best with at least some of those hours being in the afternoon. These plants need some heat and intense mid-day sun exposure in order to produce flowers and new growth.
Part shade also means four to six hours of direct sun per day but most of that sunlight should come in the morning hours, when the sun’s intensity is lower. Plants with a “part-shade” designation can struggle or get leaf-scorched in hot midday sun.
Full shade means less than four hours of direct sun per day, typically in the early morning sunlight. It can also mean dappled light below a large open canopy tree. Very few trees thrive in dense, day-long shade.