Delphinium geyeri

About

Delphinium geyeri is a species of plant in the Ranunculaceae family that is often called by the common names plains larkspur and foothills larkspur. It is infamous for causing the deaths of cattle grazing in the spring because it is especially poisonous before it flowers and so it is also called poisonweed by ranchers. It is a medium to tall plant that has very striking blue flowers and is occasionally grown in native plant gardens for this reason. It grows mainly in Wyoming with large population in northern Colorado, northeastern Utah, and parts of Nebraska.

Summary from Wikipedia