To write well about plants, we must know much about them. As when we write about a character in a story, if the picture in our head contains far more details than we spell out on the page, the reader will find and color in the gaps - because we will subtly shape the right kind of gaps.
Below is a collection of books and online resources that are good starting points for expanding our knowledge about plants. I have also included a number of photography sites and plant picture books for those of us who draw inspiration from visual cues.