"Night-blooming Cereus" is in quotation marks because several cacti go by that name. Ours is HYLOCEREUS UNDATUS. It's native from Mexico to northern South America, but is naturalized in tropical and subtropical zones worldwide. One reason for the plant's popularity is its foot-long, fragrant, beautiful blossoms -- among the largest in the Cactus Family -- but also it's grown for its edible fruits. You even see the species growing wild in southern Florida, though it's unclear whether those plants are persisting vegetatively, or actually reproducing by seeds.

If you have a "Night-blooming Cereus" that doesn't look like the Hylocereus undatus in my picture, you might compare your plant with the following species, all with huge, white blossoms, and all known as "Night-blooming Cereuses":

Epiphyllum oxypetalum: http://davesgarden.com/pf/showimage/20630/

Peniocereus greggii: http://www.desertmuseum.org/programs/images/Pengre03.jpg  

Selenicereus grandiflorus: http://www.kakteen-piltz.de/pages/010_jpg.htm

from the June 13, 2010 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO
HYLOCEREUS CACTUS BLOOMING & FRUITING
As if it weren't enough to have gloriously blooming Acanthocereus cactuses this week, our "Night-Blooming Cereus" species that grows epiphytically on trees, HYLOCEREUS UNDATUS, also put on a show, both flowering and fruiting. You can see a nice thicket of them dangling from a big Piich tree, the slender, three- angled stems bearing softball-size, crimson fruits, below:

A close-up of a fruit, rather like a red artichoke, is shown below:

You may have seen fruits like that in supermarkets up north as well as in traditional markets here. In the North they're often marketed as "dragonfruits." Cut open, inside they're mostly a white, sweet pulp in which many small, dark seeds are embedded. Sometimes here in the Yucatan you see dragonfruit plantations. You can see what the fruits look like in supermarkets as well as when they're grown commercially on Wikipedia's page about them, where they're called pitayas, at http://en.wikipedia.org/wiki/Pitaya.

Here I've found numerous flowers of this species about to flower or recently flowered, but so far I've missed them on their "big night."

from the February 7,  2010 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO
A CACTUS SEEDLING
At dusk I sat beside a forest trail as low-slanting sunlight penetrated deeply into the forest on the trail's east side. During such special, fleeting lighting situations I always hope to see a tinamous walking across the floor or maybe a Kinkajou leaving his aerial den for the night, but that day nothing really memorable happened. One thing that did happen, however, was that a large bromeliad, a Tillandsia fasciculata, for no apparent reason lost its grip on its tree branch and fell crashing through the understory to wedge in a forking branch not ten feet from me. You can see our Tillandsia fasciculatas at http://www.backyardnature.net/yucatan/tilland1.htm.

Bromeliads and orchids are always falling like that. After storms the ground might be covered with thousands of them. They may live awhile where they land, maybe even a few years if they end up where the right kind of air circulates the way they need it, for, as we emphasized in the next section, they manufacture their own food. They use the trees they're on merely as perches.

When I find such orphaned epiphytes I carry them back to Hacienda Chichen and mount them where I think they'll thrive, and in places where visitors can get a good luck at them. Thus when I left my observation spot that afternoon I retrieved the fallen bromeliad.

It was about the size of a medium dog, bearing a basketball-size wad of thick, spaghetti-like aerial roots. And sprouting out of the blackish wad of aerial roots there was a seedling so young it still consisted mostly of its two cotyledons -- those two "first leaves" that appear on many non-grass plants (the class Dicotyledonae) when they first emerge from their seed. The seedling was about as tall as the middle link of a girl's middle finger.

Usually it's hard to impossible for me to know the identity of a seedling still in its cotyledon stage, but this time it was easy, as you can see below:

Above you see a young, slender stem section of the Pitaya showing white aerial roots searching for support and finding nothing. Note how the stem is triangular in cross section, and bears short, stubby clusters of spines.

In young woods which 20 or so years ago were ranchland you don't find Pitayas but in older forest here the species is very common. Here, I'm told, they'll flower when the rainy season gets underway in June. Then during the night they'll produce foot-long (30 cm), white, wondrously fragrant blossoms.