Philadelphus microphyllus

Philadelphus microphyllus is a species of Philadelphus known by the common names littleleaf mock-orange or desert syringa. It is native to northern Mexico and the southwestern quadrant of the United States as far north as Wyoming, where it grows in scrub and brush habitat in foothills and mountains, often in very rocky areas, sometimes anchoring itself in rock cracks and crevices....read more on Wikipedia.