Patricia, your post interested me concerning how we have defined all these terms over the years, and I had always assumed that the petal count alone qualified how we call a blossom full, double, etc. But to my surprise (and perhaps no one else’s) that is putting the cart before the horse. The rows of petals, and remaining stamens determine that, and rosarians over the years have applied “normal” petal counts to those classifications. Does that mean we can possibly have a true “double” blossom with more than 25 petals? I think it does. Brent Dickerson may give us the best explanation I have found in “The Old Rose Adventurer : The Once Blooming Old European Rose, And More”:
“Roses are always polypetalous, which is to say that they are composed of more than one petal, never less than five, unless they are abortive; regular, which is to say that they are composed of parts which are similar in form and size. In the corolla, one looks at the number of petals. When they are quite lacking, one says that the flower is apetalous; should there be five, the flower is single; if there are two or three rows of them, it is semi-double; if there are many, but you can still find some stamens in the center, it is double; if there are only a very few stamens, it is very double; finally, if all the pistils and stamens have been metamorphosed into petals, the blossom is full. Collectors of roses complain that these words double, semi-double, very double, etc., do not state with mathematical precision the number of petals in a flower; but as that precision means little to botanists, because they regard double flowers as monstrosities without interest for research, these epithets have been consecrated by usage time out of mind, and have been those used up through the present.”