No, not all Sharpies are the same, nor are all permanent ink pens!

As a Master Gardener, I learned to my dismay that some "permanent" pens disappear in the sunlight after a season. "What was that plant again?" Janet Panos's answer is more to the point, but I wanted to add to the general fund of knowledge. Sharpie carries an Industrial branded pen that does hold up to sunlight, but it's not in a full array of colors. Some of the really cheap permanent pens aren't worth even the cheap cost. When you're going to invest a lot of time and talent to a project, choose your tools carefully.