I recently turned in a project for my photography class, specifically anthotype. Unfortunately it's not a "standard" process that everyone has as an assignment, rather, it was one that I chose to do myself. Anyway, I just thought that I might post my findings that petunia's work rather well for the process, especially purple petunia's (the red one's I attempted working with provided a brilliant pigment, but, the image had difficulty showing up. The reccomendation of blackberries on the "working with anthotypes" page is brilliant and was my fastest print, as well as my most detailed.
Expect petunia based emulsions (preferrably with ethyl alcohol) to take 4-5 days to print, with fairly decent contrast (as far as anthotypes are concerned). Also, petunia's do not yield a high volume of pigment, so, it takes quite a few petals to produce enough for one page. I also found that fairly sturdy papers like construction paper work well for the process, rather that lighter papers (this may have to do with the emulsion "sitting" on top of the paper, rather than soaking through).
I also found that solarizing the transparent positive you're working with (if you're not printing a plant cutting) works particurarly well, especially if the solarized image is on the darker side of things.
Anyway, just some small discoveries with anthotypes. I'll post my results when the project is returned to me.