Romneya coulteri - Matilija Poppy
This enormous poppy grows wild in the California desert. Snow white crepe-papier blooms the size of a saucer rise above 8' blue-green foliage from spring until fall. They look like fried eggs.
Plants thrive in full sun and sandy soil with no fertilizer, no water. Once established, they require no care whatsoever except to be whacked to the ground once a year so they don't take over the neighborhood. But they're nearly impossible to find.
Matilija Poppy is evergreen in zones 7-11 and even does well in coastal regions where there's lots of sun and sandy soil. The lush blue foliage is gorgeous and the blooms are amazing. Matilija looks great from a distance, is ideal for a desert hillside or neglected roadside, but is too robust for most gardens. You can contain or cut back the runners, cut the whole plant back in winter for lush spring growth, but it will soon tower over a mixed border.
Matilija is one of those rare desert plants that springs from the ashes after a wildfire and its seeds need smoke or fire to germinate. Plant them in a flat, burn pine needles on top, then water. Or soak them in smoke water before planting and they'll pop right up. These seeds came from my own plants and all should sprout if you do the smoke thing.