The night-blooming cereus is a type of epiphytic cactui that grows in trees, and as the name states, they only open at night.
The cactus itself is long and skinny, with beard-like roots hanging downwards to absorb moisture from the air, or to eventually penetrate into the earth. The flowers themselves, as seen above, are massive and extravagant looking, with a strong, fragrant scent. They tend to cluster on large trees, giving an appearance of a coral reef or something similar.
In the morning, they close up, droop, and eventually fall off.
Local residents have made a sport of cycling from tree-to-tree around the City trying to find the elusive blooms as they open, but a support group on Facebook has made it a bit easier with a crowd-sourced map of all of the known locations.
Editor’s Note: Many of these locations are on private property. Please admire the blooms from the sidewalk or public right-of-way, without invading anyone’s private space.