The good garden etiquette guide now has three entries - I found this in my Butchart garden images. It is the ceiling of one of the Japanese garden structures. As there are approximately 1 million visitors a year, this could make for the accumulation of a lot of signatures. Can you see the date at the bottom left? I think it is 1976, and there's another further right that looks like 1963. How many dates do you see?
Butchart has the best recognized garden path in North America. It is an amazing sight to experience, and everyone who steps to the edge of the rock quarry takes this signature view of the sunken rock quarry garden with the curving path leading into the distance.