I believe it's called folding or maybe pleating, its at the base of the petal and you can see the fold. When I went out to look yesterday morning, there was a bloom and I was more focused on getting a picture and posting it. After I put it on the computer and really looked at it I could see what appeared to be a small black stripe at the base of the petal. A few hours later I went back out and saw that the stripe had actually turned out to be a fold but it was only on one side. When it starts, does it always just start on the one side? The original picture is a few down 'FFO - second picture improved'. Marg