About Petrophytum caespitosum (Nutt.) Rydb.
Petrophytum caespitosum is a very low, matted shrub that forms creeping carpets up to 80 centimeters wide, growing over rocks. This species often grows on vertical rock surfaces, hanging in place via roots that cling to cracks in the rock. Its stems are thick, very short, and densely covered in rosettes of oval leaves. Both leaf surfaces are lightly covered in short, fine hairs that may not be visible without close inspection. The plant produces many inflorescences, which are spikelike flower clusters that grow from erect peduncles up to 10 centimeters tall. Each inflorescence is densely packed with individual flowers: every flower has five tiny white petals, many whiskery stamens, and usually five hairy pistils. After the flower parts dry, they may fall off, leaving behind a cluster of developing fruits called follicles that hold the plant's seeds. Petrophytum caespitosum is native to the Western United States, growing in mountainous areas ranging from the Sierra Nevada to the Rocky Mountains. It grows among limestone rocks in forested and woodland habitats, as well as on open limestone bluffs and cliffs.
