Caroline, the usual recommendation for hard seed coats like
Callirhoe is to scarify - this is easily done by rubbing seeds against a flat file. In very, very informal comparisons (just discussions in the seed-starting threads at the NARGS site), scarifying hard-coated seeds seems to give the fastest germination, and after the seeds have been scarified, it didn't seem that soaking had any additional benefit towards speeding up germination. (Note, it would be great if someone did an controlled study of this... so much of this stuff is anecdotal, including my comment, admittedly. Anyway, I believe in doing as little messing around as possible...
)
Alplains sells
C. bushii and recommends scarifying. Alan Bradshaw's advice is usually excellent.
