Calochortus obispoensis, commonly known as San Luis mariposa lily, is a rare perennial herb endemic to the serpentine soils of the coastal terraces and lower montane regions in San Luis Obispo County, California. It is adapted to the chaparral ecosystem, where it thrives in full sun and well-drained soils. The plant typically grows a slender, branched stem up to 24 inches tall, with a single basal leaf 8-12 inches long that withers at the time of flowering. The inflorescence consists of 2-6 erect flowers, each with reflexed sepals and flat petals that are yellow or orange with darker tips, measuring up to 1 inch long. The petals are distinctively fringed and coated in long, dark purple or red hairs, making the flowers quite showy during their bloom in the late spring to early summer. The fruit is an angled capsule up to 2 inches long, containing translucent yellow seeds.

San Luis mariposa lily is valued for its unique and attractive flowers, which can add a splash of color to native plant gardens, rock gardens, and dry borders. It requires minimal maintenance once established, as it is adapted to the dry summer conditions typical of its native habitat. Gardeners should provide it with low water once established and ensure it is planted in soil that mimics its native serpentine substrate for best results. While not commonly found in cultivation due to its rarity, it can be a conversation piece in a garden setting. Potential problems include overwatering, which can lead to root rot, and habitat loss in the wild due to development and land use changes.CC BY-SA 4.0