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SEASONAL NOTES: OCTOBER
This is bedtime for most cacti and other succulents, except Thanksgiving and Christmas Cacti, and other epiphytes. A cool dormancy is very important. Try to keep them close to 5oC(44oF) if possible - no lower - but at least no higher than 10oC (50oF), in fairly good light, but no direct sunlight, in the hottest part of the day, until late October, then let them have full sunlight until March.
Below about 10oC(50oF), give them NO water - NONE - until about mid March. If they get above 10oC, on bright days, mist the plants, early in the day, but lightly, to prevent shrivelling. If temperature stays above 12oC or so, mist a little oftener, but DO NOT WET the soil deeper than a millimeter or two. In a well lit, slightly humid basement, between about 8o and 12oC, they will do quite well. They should shrink a little - the accordion pleats allow admirably for that - but they should not shrivel. The closer they are kept to these ideal conditions from October to late February, the better they will bloom starting about April for some, later for others.
If you have not conditioned Thanksgiving and Christmas Cacti outside from mid June to Mid September, you should start early in AUGUST to give them their very important requirements of NO LIGHT after sundown or before sunrise, and cool temperatures, below 15oC(68oF). They are daylength sensitive plants and bloom is dependent upon the relative lengths of day and night. They require about 15 hours of darkness and 9 hours of daylight at this season. They can be fooled into blooming as if they had been kept in a natural light program, by adjusting the length of the day artificially. Put a box over them by 7pm and take it off at about 8am. Now, promise me you will condition them outside starting next June.