Orchid...cactus! Blooming the things...
 

Hi everyone! I have wanted to try keeping orchid cactuses due to their fantastic blooms, but am nervous about their blooming requirements - namely, their need for cool (cooler than 60 fahrenheit) nights for several months in fall (withholding water for most of that time would be relatively easy). Does anyone have experience with blooming these plants? If so, is the cooling period a strict requirement, or could I get away with just giving a dry period during the fall? Thank you :)

Do you mean Epiphyllum hybrids? Christmas cacti? Easter cacti? Other kinds of cacti?

Epiphyllum species. Christmas and easter cacti require cool nights and/or a drop in the photoperiod.

Most people can flower Epi hybrids if they put them into an unheated room or basement, near a window. They don't need high winter light. They will survive with damage if not watered all winter, but they probably won't bloom treated thus. They should be watered at least to keep the stems from shriveling.

If you leave them out in the fall as long as you can before frost threatens, they will probably get enough cooling naturally to flower the next spring.

They get to be quite large plants. They can be flowered in a 1-gallon pot (about 6" / 15cm across.) You can save horizontal space if the stems are tied upright into a bundle, or enclosed in a tomato cage, but the stems will be close to 3 feet / 1 meter tall. In a hanging basket the stems can easily sprawl to 2-3 feet or more out of the basket in all directions.

Many Disocactus species are ancestors of Epi hybrids, and don't require cooling. Disocactus macranthus is a relative miniature, and can be grown with orchids. Flowers are about an inch in diameter and fragrant. Disocactus speciosus (Helianthocereus speciosus) has huge shiny red flowers. It doesn't tolerate high temperatures, so it does well in cooler summer areas.

The rat-tail cacti (formerly Aprocactus, now also Disocactus) don't require cooling. They are hanging basket plants. They have smaller flowers than the Epi hybrids, but make lots of them, and they can flower all summer.

Last winter I moved my Easter cactus into a spare bedroom with southwest exposure. Closed the room heater vent and kept the light filtering drape closed (honeycomb). Watered just when segments began to get limp. Bloomed like crazy in spring with both pink and red flowers. I only remembered it having red when I bought it.

I should mention, I repotted it right after it got done blooming the year I bought it. It had doubled in size by the end of the summer and ready for its winter rest.

I should mention that Easter cactus (Rhipsalidopsis, with radially symmetric flowers) require neither long nights nor cool temperatures to flower. They will flower on typical windowsills. They don't tolerate much summer heat. Christmas cactus (Schlumbergera, formerly Zygocactus, with zygomorphic flowers) do require either 6 weeks of long nights or 6 weeks of nights below 55 F / 12C in order to flower. They tolerate warm to hot summers if well watered. Both types will grow very fast when happy during the summer.

Thanks for the info. I had read that they need cool temperatures and long nights to set buds. Since I was growing it on a bakers rack in my great room and the lights don't get turned off until 11-11:30PM that it wouldn't meet the long night requirement.

Christmas cacti need either of cool or long nights. Easter cactus don't. The plants look similar to us but they appear not to be that closely related.

I grow mine outdoors as long as night time lows are above 40°F, in a spot that doesn't get much extraneous light at night. It blooms regularly shortly after I bring it inside

These plants are wonderful for sure. We call them crab cactus. Maybe due to their segmented stems looking sort of like parts of crab claws.