Can you identify this flower?

The prairie always gives me something new to look at. But often I'm not sure what it is I'm seeing.  Here's my latest puzzle.

I realize the challenge picking out the flower and foliage from all the green. I've looked in my trusty Tallgrass Prairie Wildflower book and the closest I can come is Showy Tick Trefoil.

There are some inconsistencies between what I see in the picture in the book and what I see in real life. My prairie plant is taller than the 2-4' the book describes.  Also, while the leaves on my prairie plants are 'alternate, short-stalked, beanlike' as the book describes, they are also much longer than in the picture - 2-3 times as long.

Since I'm new to this whole prairie thing (I count three years as 'new'), I'm hoping one of you in the blogosphere will be able to help.

Or, if you're more into photography and can give me advice on how to make one green plant differentiate itself from all the surrounding green plants, I'd be grateful for those tips, too!

Thanks!