This is one of the "Crazy for Birthdays" series, stitched for October last year - with the opals included! That one was fun, and I think I have a description of how it was achieved under the label on the side for Birthday Crazy Quilts or something.
Anyway, I studied not only the real thing growing in the flower bed, but looked at a lot of pictures, as that seems to be the most efficient way of replicating the "look" of flowers in silk ribbon.
I used 4mm ribbon for these, as the petals aren't quite as fine as the asters for September - on which I used 2mm ribbon. The little centers are made with French knots and Soy Luster.
Creating with silk ribbon for surface enhancement is almost instant gratification, and one only needs to learn to handle the ribbon - it's qualities and limitations. Just a few basic stitches are all I've found necessary to make flowers that at least resemble what I wanted - and it's great fun to study leaves and flowers, vines, etc. outside, and figure out how to do them in silk ribbon. I even did a series of Texas Wildflowers several years ago! (can't find them now)