The tops dont have chlorophyll (which would make them green or normal colored), so they cant make their own food. I heard once that they were irradiated to kill the chlorophyll, but that might not be correct....
Mike

There is a very interesting story behind these little buggers.
It all started with only 2.
Read on...
http://www.lapshin.org/cultivar/N12/histor-e.htm

Matthew

Here is a link that might be useful: History of Gymno. 'Hibotan'

Thanks ! Was wondering how come you never see just the colored tops.....lol

Matthew,
Thanks for the link and info. I was told a long time ago that the 1st. red headed cactus was a result of the bomb blast that ended the 2nd. world war. Thanks for setting the record straight.
Stush

Matthew,
Do you happen to know what stock they graft these to. I had one that the top died and the bottom grew out like a vine. I ended up giving it away. Sorry I did now.
Stush

I think they are mostly Hylocereus but they will do well on other stocks as well.
Matthew