These dramatic California natives are one of my favorites. Matilija poppies (Romneya coulteri) are difficult to get established, but once they decide they like a place, watch out. They grow about 8 feet tall and spread into huge clumps—they are aggressive. I have them growing in a large raised bed next to our driveway. You'd think that would contain them. Not quite, they are constantly trying to send up shoots through the tiniest chink in the asphalt driveway. The only plants that have survived in the bed as their neighbors are bougainvillea and a large jade plant (Crassula ovata). These plants are left to fend for themselves. Most of the year it just looks like a jumble of overgrown and untidy plants.
Then come May, the Matilija poppies erupt into bloom and remind me why we put up with their aggressive ways the rest of the year. The flowers are big, about the size of your outspread hand and so stunning. Here's a slightly closer shot.
You can see how the bright yellow pollen is staining the white petals. I've not tried using them as cut flowers because I think they would be a bit messy. So instead I just enjoy looking at them every chance I get during the month of May.