Updated: May 9, 2020
Now this can get confusing, but to get the best results with your plants, the rules of thumb are outlined below:
Full Sun is six or more hours of direct sun a day. Full Sun plants like bright sunny areas – many full sun plants will be perfectly happy with 14 hours of sunlight every day.
Partial Sun or Partial Shade is four to six hours of direct sun a day. This is probably the most confusing category. The two terms are fairly interchangeable. These plants prefer four to six hours of sun a day and would be happiest getting their sun mostly in the morning and/or evening with shade through the middle of the day. If a plant is called partial sun the emphasis is on making sure the plant gets at least four hours of sun a day. If a plant is called partial shade, then greater emphasis is placed on the plant not getting more than six hours of direct sun.
Full Shade is less than four hours of direct sun a day. Full shade plants prefer to get little direct sun. They like less than four hours of direct sun a day and prefer morning and evening sun to mid-day sun. Full shade plants should also do outstanding in dappled shade conditions. An area that will be shaded by a fence or wall will need to get several hours of sun in either morning or evening for plants to do well. Full shade does not refer to dark places, all plants need at least some light.
You may also see the term Dappled Shade. Dappled shade refers to areas where there is a mixture of sun and shade, generally because a deciduous tree is nearby. Dappled shade is similar to partial shade. Plants in this category are often woodland plants and will do best with little full sun (every morning or evening sun).