Romneya coulteri has grey-green leaves which are pinnate (leaflets arranged on each side of a central stalk) and large, 'fried egg' flowers which are scented and have 4-6 'crepe paper' petals and many rich yellow stamens.
Romneya coulteri is known as being highly drought tolerant when established, and likes full sun. If this plant is happy, it will spread quite aggressively by underground runners. Matilija Poppies commonly go deciduous in summer or fall and come back in spring.