Hi,
I wonder if someone could help me identify this Cacti please?
I'm in Sydney, Australia, and I have this in a pot in my back yard. It flowers spectacularly at night, this time every year.
Photo here: http://pg.photos.yahoo.com/ph/womb8t/de ... m=da54.jpg
I believe it may be a South American - 'Cereus chalybaeus'?
Thanks and regards,
Kevin Searle
Sydney
Help identifying night flowering Cacti - Cereus?
I'm afraid, you won't be able to get a positive ID on CactiGuide either. 
You have a cactus that is arguably the most common yet least studied of all cacti. I think this paradox stems from people's natural preference for scarce goods. I have yet to see any source that deals scientifically with the many Cereus plants in cultivation accross the globe. Your cacti almost certainly is a product of cultivation and does not exist in the wild. Because there are so very many people who like to grow plants, but couldn't care less about proper names or origins, tracing back to parent plants is no longer an option. That is short of comparing the plants DNA. However, the guys with the laboratories and know-how at their disposal to study the DNA have been studying unusual and uncommon species such as Aztekium or Eulychnia. This brings us full-circle. Perhaps someday the right Biology student will decide to do a thesis on the "Origins of Cereus" and we'll all get lucky. In the mean time you can probably get away with using the "garbage can" name of Cereus peruvianus or simply Cereus species.
You have a cactus that is arguably the most common yet least studied of all cacti. I think this paradox stems from people's natural preference for scarce goods. I have yet to see any source that deals scientifically with the many Cereus plants in cultivation accross the globe. Your cacti almost certainly is a product of cultivation and does not exist in the wild. Because there are so very many people who like to grow plants, but couldn't care less about proper names or origins, tracing back to parent plants is no longer an option. That is short of comparing the plants DNA. However, the guys with the laboratories and know-how at their disposal to study the DNA have been studying unusual and uncommon species such as Aztekium or Eulychnia. This brings us full-circle. Perhaps someday the right Biology student will decide to do a thesis on the "Origins of Cereus" and we'll all get lucky. In the mean time you can probably get away with using the "garbage can" name of Cereus peruvianus or simply Cereus species.