We usually think of legumes as forage crops but they also make nice subjects for photography. In the Midwest they mainly consist of alfalfa, clover and vetch. What I like about photographing them is that they start blooming around the first of June and continue to bloom until killed by frost. This year they were blooming by the middle of May. All of the above mentioned legumes are blooming in my prairie area. In order to keep them blooming I mow them periodically so there are always some blooming and always some blooms for the butterflies and bees.
The great thing about alfalfa is that it comes in a wide variety of colors. Almost every plant offers a different opportunity for photography.
Clover really lends itself to some great photography opportunities when there is a heavy dew.
Vetch is a less common legume but it still provides a nice subject for photography.