Melanie Mason, N.Y., in response to Jamie Gossard “Re: Ripped edges… although visually I agree with Jamie Gossard that the edges have a torn appearance, if you look carefully, the color of the toothy edge persists completely around the petal, with no interuption. My thoughts are that at somewhat regular intervals along the edge, there is cellular proliferation. At these intervals, the edge grows faster than the petal, allowing teeth, knobs, horns, and even tentacles to appear. Nevertheless, even in the absence of these protrusions, the edge is apparent.”
Melanie's comments make sense and so I assume then that cellular proliferation is a genetic trait because some toothy cultivars have no toothy "lineage." And I think high humidity may cause teeth to be more pronounced.