The "anemones"

Agaves 

Flanked by smaller agaves, A. parryi truncata appears to wait for prey to glide past. This powerhouse succulent (as large as 2 to 3 feet tall and 3 to 4 feet wide) and its smaller brethren are tough enough for desert gardens; plant them in full sun in all but the hottest climates. ‘Bloodspot’ mangaves drift in the agaves’ wake, adding their own edgy interest and dappled patterns to the sea-bed scene.