It varies from plant to plant. Evergreen perennials require light throughout the year. Come-n-go perennials like flowering bulbs only need sun when they have living above-ground foliage. In general, if the plant has living foliage, it needs light to stimulate photosynthesis.

.... and then you wonder - - what time of day are they talking about. I mean we get warm sun as early as 8 in the morning - and goes on until dawn... In the South six hours could toast some plants - I think it is just trial and error with some plants needing a certain amount of sun.

I know from experience now that I am living in the South that six hours here and so different from six hours in New York.

Carrie

I second that thought Carrie! Many things that I thought loved full sun, like peppers and some of my herbs, were frying in our high altitude full sun. The peppers in pots on the porch, which is shaded a good part of the day, are doing MUCH better than the ones in the vegetable garden. The problem I have is that there is only so much room on my porch, so I try to plant things that can REALLY handle all day full sun.

Mary, your climate is very similar to mine. I would bet if the label says 6 hours of full sun, it would do fine with much less than that where you are.