Cleistocactus buchtienii grows as a shrub with branched, rigid shoots at the base and reaches heights of growth of up to 1.5 meters (rarely up to 3 meters) with a diameter of up to 5 centimeters.

There are about 16 to 19 (rarely up to 22) low ribs present, which are conspicuously notched.

The radial spines, which are 8 to 15 to 2 centimeters long, are slender and spread out.

The tips of the bracts are burgundy or greenish to dark green.

The spherical fruits tearing open at the base reach a diameter of 2 to 3 centimeters.