This was a absolute can't-pass-it-up-on-the-interstate flower. Fortunately, there were enough of them that I didn't have to back up. That 2013 trip was a good one for cactus, and this was the hands down winner. The flowers are about three inches across, and may be yellow, magenta, or this combination. This is an important food plant for prairie dogs and other wild grazers. Ranchers sometimes burn areas where it grows to remove the spines. Its nutritional value to cattle is as good as alfalfa. It grows in AZ, CA, CO, ID, KS, MO, MT, ND, NE, NM, NV, OK, OR, SD, TX, UT, WA, WY, AB, BC, and SK. Logan Co CO, 6/16/13.