H 2 cm from seed. Pediocactus knowltoni is a very small plant (one of the world's smallest cactus) usually solitary or a few in a cluster barely protruding above ground level.
It has a unique growth pattern that facilitates avoidance of desert droughts and high temperatures. Generally there are 2 growth periods in a year. In the early spring (April-May), plants grow, bloom, and set seed. From June to September, aboveground growth stops, and plants shrink into the ground. Summer dormancy is considered "very definite". Cultivated plants receiving supplemental water also experience summer dormancy. Root growth continues when aboveground plant parts recede into the ground. After late summer rains, it cactus grows again. "Offsets", or new stems, are often produced at this time. Often flower buds are produced in the fall; buds remain unopened through the winter.