We were wondering about these two cacti given to us by friends. The tall one on the left seems to want to branch (we got a cutting off a 3-4 foot tall potted specimen). The short guy we think is a gymnocalyceum, and have always been a bit puzzled by its odd coloration (kind of dayglo yellow and pink). It was potted in fine sand and really suffering when we got it 2 years ago. Not sure what either of their specific needs are (minimum tolerated temp, sun exposure, etc).
Thanks for your help!
The tall one is a Cereus. The short one could be a Gymnocalycium, but I wouldn’t know for sure until it blooms. The coloration seems to be an effect of the sun and probably the soil too. It can handle less than full sun, and may need to be repotted into fresh fast draining cactus soil in the spring.
In the San Francisco area I would recommend watering every 2 to 3 weeks through the summer, less in winter. They are probably hardy down to about 30F.