Clematis hirsutissima is a species of flowering plant in the buttercup family known by the common name hairy clematis or vase flower. It is a perennial herb that is native to much of the western United States, from Washington to Nebraska. It is a small, erect plant which, unlike other Clematis, does not generally produce vines. It is quite variable in appearance, especially across varieties. In general the hairy stem reaches up to about half a meter tall and has many large hairy leaves divided into lance-shaped lobes. The inflorescence appears at the tip of the stem and bears a solitary flower. The flower is made up of an urn-shaped cup of deep purple-blue petal like sepals, which are fuzzy and have pointed or rounded tips. Rare individuals have white or pinkish sepals. There are no true petals. The fruit is a hairy achene with a very long beak and a plume on the end; it is dispersed by wind.

The roots are large, deep reaching, and many branched. They produce a large crown with many dormant buds. It is often dormant in summer.

It grows in grasslands, sagebrush plains, and ponderosa forests.

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