I know these aren't Zygocacti, for Heavens sake... discounting those (which deserve their own blog by someone who can actually grow them well) I realize that Christmas isn't exactly cactus season (except maybe in Patagonia)...but there is something terribly Christmassy to my eyes about the flowers of the myriad claret cup cacti (a section of Echinocereus that is distinctive for its badminton birdie flowers that stay open rather than close at night like most echinocerei). A dozen or more species have been named in this section of the genus based on their genetics and distribution: one of the most spectacular, Echinocereus polyacanthus, is found primarily in northern Mexico--but has proved very hardy at Denver Botanic Gardens for twenty or more years. It has especially lovely, immense crimson chalices--a rich claret cup indeed! Cheers!
This is one of the many fine cushions of E. coccineus at Denver Botanic Gardens Dryland Mesa.
For contrast, here is a form of Echinocereus gonacanthus (probably best treated as a form of E. triglochidiatus) on Dryland Mesa as well: I have admired large mounds of these on the cliffs at Royal Gorge, not far from Canon City in central Colorado.
And here is the giant of the group: the huge "White Sands Form" of Echinocereus triglochidiatus. This performs quite a ballet in the garden, rising to great heights in summer, and shrinking to half its summer height in winter. I remember seeing this everywhere around White Sands in the 1970's and nary a one on a recent field trip: were they hiding? overcollected? was I just in the wrong spots? I have observed areas with widespread cactus die off periodically (they succumb to prolonged drought or insects as other plants do--and will come back). One of the above no doubt is correct. Fortunately, my buddies (Dan and Socorro) at Rio Grande Cactus grow this by the thousand! (I blogged about their enchanting nursery a few months ago).