Try posting your question on the cactus/succulent forum. I've never heard of such a cactus, but then I've only been a cactaholic for a few years now. I, too, would love to know about this "night blooming cactus" business...

Shelly

The name of at least one of the night blooming cacti is Seleniarius grandiflora, or Cardon, as it is commonly known.

Found some pictures, too. These two websites seem to be photographs of different plants, although the flowers are similar, and so it may just be that different growing conditions have modified how each plant has grown. The first site shows a plant that is significantly fatter than the one on the other site, and whose plant seems to have less, and shorter, spines.

Here is a link that might be useful: Night blooming cactus #1

This site actually names the plant, and has a much better quality picture.

Remember, though: it's really hard to get cacti houseplants to flower. So if you set this one outside, there's no guarantee that it'll flower. Living in Maine, your plant would have to be treated as a houseplant that you would put outside just for the summer months. In my experience, this kind of climate (house temp to summer heat) isn't condusive to flowering.

Here is a link that might be useful: Seleniarius grandiflora

Did a search for this alleged "night blooming cactus" on desert tropicals, and found one called Peniocereus greggii. This one is apparently hardy to -6 degrees C. (20 degrees F), and can handle light shade. It's also called Night Blooming Cereus, Reina de la Noche, or Arizona Queen of the Night.

Here's a picture, but that has no flower:

Here is a link that might be useful: Peniocereus greggii

The desert tropicals site won't let me link directly to the page with that plant on it. The link above takes you to the site's home page, so on the toolbar on the left, you'll need to click on "succulents", and then search in the alphabetical index for Peniocereus greggi. Sorry about that.

Hi just logged into this sight. is there another Seleniarus grandiflora? I have two types here. One has three ribs, the other four, like the one in the photos by fishies. They have the same flower. The four ribbed one flowered about 6 years ago. The three ribbed one has two buds on it now. It's about 6 years old also, grown from a stem cutting. This is it's first time flowering. Any info would be appreciated.
Cheers Jancc

Cactus that flower at night usually have white flowers. eg species of Cereus and most of the Trichocereus. There are Trichocereus with yellow or red flowers too. White flowers are usually bat pollinated plants. Therefore don't need the colourful flowers to attract insects. I grow many of these plants in Australia and the flowers open at night but will stay open for two or more days and the bees love the copious pollen they have. On a warm summers evening the wonderful perfume of the Trichocereus flowers is quite an experience. You can tell the difference between a Trichocereus and a Cereus by the flower stalk. Cereus are smooth and the Trichocereus buds and flower stem parts are quite hairy. Tricho. flowers can be picked and put in a bowl (no water needed) in the house and will stay open for several days and perfume the house! Cereus flowers will wilt if picked. Joylene. Australia!