I came across an article written in 1997 about shade gardening by Tony Avent
"There are as many theories to explain our love of shade garden as there are people to espouse the theories. Perhaps it is our longing for enclosure that is satisfied with the canopy of a tree, or perhaps it is simply the search for a cooler spot on a hot summer day. Ironically, visitors from countries like England always migrate to the sunnier beds...perhaps tired of their overcast perpetually misty climate. I am always amazed how few shady gardens there are in England.
When we talk about shade, we all have our own ideas about what is shade. I like to begin by explaining that all shade is not created equal. It's sort of like going to the store and asking for white paint. A clerk will quickly respond, "Do you want flat white, glossy white, antique white, eggshell white, clear white, or what?" You see, all shade is not necessarily the same.
I like to define shade by using several categories: morning shade, afternoon shade, light shade, and dense shade.
Other than the age old issue of soil preparation and enough irrigation to account for the tree roots, the recipe for successful shade gardening lies in the correct plant selection."