Different artists depict flowers differently and not all of them appeal to my eye. I am very much attracted to Sharon Hinckley's painting style. I am a fan of the bright colors of Gauguin and the vivid up-close and personal semi-abstract flowers of Georgia O'Keefe, and although they both mostly worked in oils, I think Hinckley has merged elements of both of their styles with her own and produced some wonderful watercolor painting.
Watercolor painting is more difficult than oil painting because you can't really paint over your mistakes without making a mess. Hinckly not only explains how to create flowers step by step (beginning with a discussion of the appropriate supplies and an explanation of color), she shows the reader how to make what she describes as "leaf soup" which forms the basis of the foliage in her watercolors. Hinckly says while many would-be artists can create flowers, most have difficulty with the stuff that grows with flowers, i.e. leaves, stems, and bark. One photo shows Hickley's palette, "leaf soup" mixture.
There are many books on the market offering instruction on "how to" draw-paint flowers, but if you are fond of the "colorist" approach to painting, you may find it hard to beat the techniques described in WATERCOLOR BASICS, PAINTING FLOWERS.