Rick
Well-Known Member
Marco said:Antec has a great list on which paphs need calcium supplement. http://ladyslipper.com/calsub.htm
Just to add a bit onto the fertilizing question. What's the difference with fertilizers with and without urea?
Thats not really a list of species that require calcium supplements, but a list of species that are found in association with calcareous environments. Refer back to my post on pH.
Urea is a nitrogen yeilding molecule that is somewhat more complex and less bioavailable than ammonia. Some orchids apparently find it difficult to consume and sometimes toxic. Ammonia and Nitrate are the easiest nitrogen forms for orchids to utilize. Ammonia can be toxic at pH levels from 7.5 and up. So if you wanted to buffer up the fertilizer mix for a roth to duplicate the ultra basic conditions of serpentine (the geology that roths are found over) the pH could be greater than 8, and you should use a nitrate based fert rather than ammonia.