I've found a great Android app for wildflower ID. Wildflowers of Tennessee is the name, and though it is specific to this state, I expect there are similar ones for other areas. You can select for color, number of petals, month, area of state and other criteria. As you add details, the choices narrow down to a manageable number and there are good photos of each flower. It's another fun thing to help enjoy the outdoors.
Trillium attached.