Both native to beach areas in regular sandy beach soil, though can grow in sandy loam soil too.  Beach Primrose(yellow flowers) blooms year-round.  Takes regular irrigation, which is necessary for good appearance and abundant Summer-Fall bloom, but survives on rainfall alone in the wild, and in moderate domestic situations.  Beach primrose is usually low and spreading, but some plants grow as a small bushy subshrub.  Ambrosia is reliably low and spreading, has the upright brown-green flower stalks; btw, Ambrosia has sharp burr 'fruits' that scatter, - they hurt to pick up.  The grass poking out from the sand is Distichlis spicata.  Photo at San Diego River ocean outlet, east Dog Beach.