The name, Moon Cactus, is a commercial name that seems to appeal to kids, who are probably the No.1 fans of these bizarre specimens, beating out the second largest group--vacationers picking up last minute souvenirs in airport gift shops across the Southwest.
Moon Cacti are not a genus. They are result of a cactus graft. The colored tops are not normal—the colors occur because the cactus does not produce chlorophyll. The combination is necessary because the top cannot survive without chlorophyll and the bottom supplies it. Usually the colored top of the joined specimen is a Gymnocalycium mihanovichii var. friedrichii and the bottom a Hylocereus trigonus, but there are also other combinations in many colors.
My little arrangement will never see direct sunlight because the sun would fade out the color. The colored part is also easily sunburned, so this little grouping will live under my patio for the rest of its natural life.
The moon is at her full, and riding high, Floods the calm fields with light. The airs that hover in the summer sky Are all asleep to-night.
~ William C. Bryant
The moon will turn full on May 31, 9:04 p.m. Eastern Daylight Time.