Sacred datura NPS/Robin Hampton. Paintbrush NPS/Pete Sawtell. Large, delicate flowers like the sacred datura (Datura wrightii) and Bridge’s evening primrose (Oenothera longissima), which wilt in the heat of the day, bloom at night in cooler temperatures. Others, like the datil yucca (Yucca baccata), have flower petals with a waxy coating. A waxy coating, or cuticle, allows the petal to retain water and withstand the drying heat. Still other desert survivors, like elkweed (Swertia radiata), bloom in the high elevation of Zion’s plateaus where the temperatures are cooler and rains are more frequent.