During our various excursions, we had the chance to discover a large number of flowers, starting with those of cacti. I feared that we were a little late in the season to see so much.
Discover and contemplate is good, but identify them (or at least try) is even better. Having had a collection of hardy fuchsias over 100 different varieties, I know a little bit the question.
We started by on the spot buying a book (see page bibliography) in Tucson. Then, whenever possible, we took photos with the names of plants. Such as the photo of the top of this page, or this one:
This kind of pictures has, of course, no artistic value but is rich of information for us.
But the bulk of the work was done at home, during the drafting of our report. We deliver below the links we used to try to identify our samples.
For some flowers, such as that found in Arches at Double Arch, it was much harder and I had to call for help on the net for Americans. It turns out that this is a rare plant, endangered.
An interesting discussion (in French) is on VoyageForum: Flora of the American West in May ... and associated photos.