Last year I picked up more than a dozen pots of Thanksgiving Cactus for about $7 which was outrageously cheap. I grew them all year giving them as much outside time as possible, so they were outside from roughly April till early November here in Central Texas.
Schlumbergera are epiphytic cacti and thrive in shade, humidity, and quick-draining soil. Wait, what? Humidity and quick-draining soil? Despite what some sources say, they do not like water-retaining soils, and I have the rotten plants to show for it. They are in the Cactaceae family after all. They come from tropical jungles and grow in the trees much like epiphytic orchids, and also like orchids, they like a coarse "soil" and humidity. Their roots will rot easily if you give them a potting soil rich in compost and peat moss.
Towards the middle of October, my Thanksgiving Cacti started to bud as the daylight hours shortened and my watering regime lessened. I submitted this particular planting to a garden show competition and got a Green Thumb (the equivalent of an A+). I might have taken a "Best of" had it been fully in bloom rather than just budding. Of course, it started blooming a week after the show, and they've been blooming and setting new buds ever since. For the rest of the year, they look like a pretty green lawn of non-threatening cacti which is very attractive in my opinion.
This Instructable shows how to mix an organic cactus potting soil, repot a Thanksgiving/Christmas Cactus, take advantage of after-Christmas plant sales, and prepare an extravagant planting for next year. I'm doing this on a smaller scale as I already have a huge planting and have spent the past year experimenting with the plants. However, once you know how to prep the pot, mix the potting soil, and separate the plants, you can easily create a huge planting of them. Like most inexpensive, DIY gardening projects, you have to wait to reap the benefits, but you will have something spectacular in the end. I worked on a single planting for a year, and I don't regret it. I have other plantings that will take decades. Consider this "quick" when it comes to plants and gardening in general.
Note: I say "cacti" rather than "cactuses" out of personal preference. Spelling nazis can argue the finer points of which is correct.
Note: I am using plants in this Instructable that are budding/blooming which is something you do not want to do. The blooms and buds are very sensitive to movement and will drop off easily. Wait until the plants are done blooming before repotting so you can enjoy them for as long as they last - there will be plenty of time to see them without the blooms/buds.
Note: As with many gardening how-to's, there's going to be disagreement. Many gardeners, including myself, are reluctant to be explicit in how to care for plants because it's more art than science, but if it weren't for gardeners willing to be explicit, I never would have tried because it would have required too much mysterious gardening voodoo. In the end, you're going to develop a sense of how to best care for a plant by feeling it out and trying lots of different things, and depending on how you garden, you might have to adjust some of the things I suggest.
Step 1: Mix Cactus Potting Soil
1 Part Builder Sand
1 Part Pea Gravel or Perlite
1-2 Parts Compost (preferably your own)
Take a container (tin can in my case) and fill with sand. Pour into a large bucket. Repeat for the gravel and compost using the same container.
Note: You will need enough to fill the pot.