Mary-Louise,
Not sure where you're located, but if you're in the Northeast, I really like Newcomb's Wildflower Guide for flowers in bloom. For quicker ID for the most common species I like the little Nature Study Guides, like Fern Finder, Tree Finder, Winter Tree Finder, etc. I haven't yet found a good guide for leafy plants like grasses or flowers not in bloom, myself, though. I've heard the iNaturalist app can also be a useful tool, though I've never used it myself.
By the way, I love your drawing style, especially the way you rendered the flowering plant, and I love the faint leaves in the background of the grassy plant- gives atmosphere and hints at the wildness of the plant!