Carnegiea gigantea

The flowers open after dark, sometime around eight in the evening, and they're finished by the following midday. A saguaro flower gets one night and part of one morning, and then it's done for good.

That schedule is built for bats. The lesser long-nosed bat winters in central Mexico and moves north each spring along what biologists call a nectar corridor — a chain of blooming columnar cacti and agaves that opens in sequence, so there's always something in flower ahead of the flight. The bats arrive in southern Arizona as the first saguaro flowers open and follow the bloom north. They hover, plunge face-first into the flower, and carry pollen forward with them.

The morning shift belongs to white-winged doves and native bees, which is why the flowers stay open a few hours past dawn. Between them, a saguaro gets covered.

The bat was listed as endangered in 1988 and removed from the list in 2018 — the first bat species anywhere to be delisted after recovery. Roost protection on both sides of the border did it.

A saguaro takes about ten years to reach an inch tall, fifty to seventy years to grow its first arm, and can live past a hundred and fifty. Nearly all of that time is spent as something you'd walk past without noticing.