Peniocereus greggii is a slender-stemmed cactus with a large underground tuber that can reach the size of a basketball, and weigh as much as 15 pounds. Occasional specimens are known to weigh as much as 87 pounds. It is reported that native Americans utilized the tuber for food. The grey stems are four to six ribbed, to 12 mm in diameter, and resemble the stems of the shrubs that often support them. The stems are armed with short dark spines along the ribs. Flowers are large and beautiful, salverform, nocturnal, scented, white, to 7.5 cm in diameter. They last only one night. Fruits are red, ovoid, sparsely spiny, fleshy and many-seeded. ... The known range [includes] large areas in central Arizona, southwestern New Mexico, western Texas, and south into Sonora, Mexico at elevations below 4000 ft. from the website of The Desert Botanical Garden, Phoenix, Arizona
I smelled the beautiful scent of the flowers as I turned the corner on my Wednesday morning walk. Much to my surprise, there were only four blooms. In other years, the plant has been covered with them.

The next day, of course, the blooms had shrivelled.