I started my collection of Christmas/Holiday cactus a few years ago also. I found information with pictures that helped me identify at least the different stems. I found it under History of Christmas Cacti.
S.orssichiana has wide, large and shaply serrated stem-segments ( #2) Blooms end of August or Sept.
S. truncata has stem-segments of similar shape but a little bit smaller. It blooms in Oct. and November.
S, russelliana has rounded and nonangular stem stegments ( #1) smaller than the previous one. Blooms from Jan. to Feb.
S. opuntioides has steeem segments looking like small Opuntia stems (#3) It blooms March or April
These four species were discovered during a period that extends from 1819 to 1978.
If I could find the link I would share it, but as usual it has gone to cyber heaven.
If the picture does not show the entire leaf, I will be happy to privately email you the picture if anyone is interested in having it.
I have quite a few and have them listed in Plant Scout on Daves Garden. I am trying to eventually bring that information here, but it is quite a job. I am always looking for someone to trade with, but I would appreciate only trading identified plants. I am trying to identify an old heirloom given to me that is supposed to be orange with a pink center. To do it properly is so time consuming.
I hope you all enjoy the information and please feel free to contact me with any questions. I am still learning and will continue to do so. But, I am willing to share information anytime.
