Calyptridium umbellatum is quite a distinctive species; plants produce one or more small, basal rosettes of spatula-shaped leaves from which rise a single, purplish, leafless stem, topped by a dense, spherical cluster of several dozen pinkish-purple flowers. Leaves are usually around 2 inches long but can be up to 5 inches. Stems are leaning. Leaves and stems are hairless.
The small flowers have two round, white or pale pink sepals, four oblong petals, three stamens with yellow or red anthers, and a thread-like style with two stigmas. The petals and sepals are approximately equal in length. The flower cluster is between 2 and 3 inches in diameter.