"Full sun" and "part shade" on a plant tag are more precise than they sound — and worth actually measuring.
What the Labels Actually Mean
Full sun means at least 6 hours of direct sunlight a day; part sun or part shade means 3 to 6 hours; full shade means less than 3 hours of direct sun, though many "full shade" plants still want some bright, indirect light. Watching a spot for a full day, and noting how many hours it gets direct sun, is more reliable than guessing.
Reading a Plant's Signals
A sun-loving plant getting too little light often grows leggy and stretched, reaching toward the nearest light source, and blooms poorly. A shade plant getting too much sun typically shows scorched, bleached, or crispy leaf edges, especially in the afternoon.
Light Changes Through the Season
A spot that's full sun in early spring, before deciduous trees leaf out, may become significantly shadier by midsummer. Reassessing a bed's light levels once trees have fully leafed out gives a more accurate picture for choosing plants.
