This clover stands apart from other low-growing white ones by having a wooly head, hence the name woolyhead clove (Trifolium eriocephalum). It grows at lower elevations, often in wet meadows or pastures. It is found in the western U.S.
For more info on woolyhead clover, click here.
I found this clover under some mixed conifer near a spring when I went hiking the other day. It's longstalk clover (Trifolium longipes), a member of the Pea Family (Fabaceae). It's found throughout the western U.S.
For more information about longstalk clover, click here.
This tall spreading plant in the pea family (Fabaceae) growing along roadsides is white sweet clover (Melilotus albus). It is native to Europe and Asia but was brought to North America in the 1600s and has become invasive. It is sometimes included with Melilotus officinalis, the yellow-flowered similar looking plant.
The flowers are white and grow in tall, narrow clusters.
For more information about white sweet clover, click here.
This attractive blue flower is silvery lupine (Lupinus argenteus), a member of the Pea Family (Fabaceae). It is native to western North America and grows in sagebrush, grasslands, and forests.
Flowers are clustered and bright blue.
This long-flowering plant can grow up to 3 feet tall.
This dainty Pea Family (Fabaceae) flower is spiny milkvetch (Astragalus kentrophyta). It grows above 10,000 feet in elevation, and is native to western North America. It has pointy leaves that somewhat resemble spikes.
This tiny milkvetch found above 10,000 feet is balloonpod milkvetch (Astragalus whitneyi). As you might guess by the common name, the seed pods are big and inflated. 
The small flower is 5-petaled, mainly white with a hint of pink or purple with darker lines on the banner.
A plant sprouting at elevations below 6,700 feet in this area in shrublands, and along streams and ditch banks is American licorice (Glycyrrhiza lepidota), a member of the Pea Family (Fabaceae). It is also called wild licorice, and has a licorice-smell to it and the stems are often sticky. 
The entire plant has been used for medicinal uses (click the link to learn more). The root of American licorice contains 6% glycyrrhizin, a substance 50 times sweeter than sugar. 
This plant with the three leaves and clover-like yellow flower is in the Pea Family (Fabaceae) and is called Black Medick (Medicago lupulina). It's in the same genus as alfalfa, and also non-native. It is from Eurasia and Africa.
Photo taken 5-21-09.
This striking yellow flower in the Pea Family (Fabaceae) growing next to streams is prairie thermopsis (Thermopsis rhombifolia). It is also known as golden pea, golden banner, false lupine, and prairie goldenpea.
The yellow flowers are usually grouped with 7-30 on a loose raceme.
This little flower is hard to see, nearly covered by the three-leaved clovers providing shade. This is a member of the Pea Family (Fabaceae), and is hollyleaf clover (Trifolium gymnocarpon). 
The flowers are white with just a touch of pink. They grow at a wide variety of elevations, including sub-alpine.
As the genus name Trifolium suggests, many of the leaves are in groups of three.
This plant can spread and become a mat on the soil. It is easy to miss.
This Astragalus looked different from the Astragalus newberryi I had seen a couple weeks earlier. With its bushier form, more upright stems and flowers, and greener leaves, I knew it was a different species. There are plenty of choices, as Astragalus is a big genus within the Pea Family (Fabaceae), but I was able to key it out to Freckled Milkvetch (Astragalus lentiginosus).
The purple and white flowers are abundant.
The seed pods have a deep crease and a beaked end--apparently one of the distinguishing characteristics.
When I saw this flower, I knew immediately the plant was in the Pea Family (Fabaceae), and I guessed it might be an Astragalus. But I had to look closer.
What I saw was that at the end each leaf, there wasn't a leaflet, but rather these tendrils, making this instead a Vicia, in particular American milkvetch, also called common milkvetch,or wild pea (Vicia americana). 
After flowering, the plant will produce pods that contain a couple of pea-like seeds.
This widespread plant can be variable in size and shape of flowers and leaves. The leaves on these specimens were broader than some of the other photos I've seen on the Internet.
When a patch of purple caught my eye among the sagebrushes, I couldn't help but run over to it, my heart pounding fast. Sure enough, it was a new plant for the year, my first sighting of it. I recognized it as a milkvetch and took out my key. Then I groaned. There are 26 milkvetches in this area. I did my best to key it out and match it with photos, and I'm fairly certain this is Newberry's Milkvetch (Astragalus newberryi), in the Pea Family, Fabaceae. 
It was growing near a sagebrush on gravelly soil.
The leaves and calyx are hairy. 
