When composing a proper compost, one often faces the question, addition of limestone or not? Although many paphiopedlums grow on or adjacent to limestone itis claimed by some authors that the never grow on the rock itself, merely in the moss and debris covering the moss. Well, to be brief, during the last couple of years, I have used a compost mix that is composed of more or less entirely of marble chips supplemented with coarse dolomite and a little sand and bark. The results can be seen in these thread:
http://www.slippertalk.com/forum/showthread.php?t=28212
Recently I have reconsidered the opinion about marblebeing more or less inert, it does i crease pH rather quickly I have noticed in tests with water plus a grain or two of marble, minutes. Also doing potting of some of those composts, I have found a big difference i. Root growth. So, depending on whether the roots grow into this limestone gravel mix, the following has been seen:
1)paphiopedilum whose roots do not mind limestone gravel:
Malipoense
Micranthum eburneum
Tranlieanum
Vietnamense
Helenae album
Stonei
Armeniacum
Emersonii(?)
Hangianum(?)
2) uncertain status based on observations roots in limestone mix
Topperii
Charlesworthii
Esquirolei
3) those that do not grow roots in limestone mix
Rothshildianum
Jackii(???)
Anitum
Randsii
Well these are based on my observations on seedlings. Seems as if parvis are quite tolerant, the others are more questionable. Based on these observations I have decided to use more bark based mixes, my favourite has for many years been the pretty good mix of Lance Birk; 8parts bark, 2parts sheet moss and 1part sand.
http://www.slippertalk.com/forum/showthread.php?t=28212
Recently I have reconsidered the opinion about marblebeing more or less inert, it does i crease pH rather quickly I have noticed in tests with water plus a grain or two of marble, minutes. Also doing potting of some of those composts, I have found a big difference i. Root growth. So, depending on whether the roots grow into this limestone gravel mix, the following has been seen:
1)paphiopedilum whose roots do not mind limestone gravel:
Malipoense
Micranthum eburneum
Tranlieanum
Vietnamense
Helenae album
Stonei
Armeniacum
Emersonii(?)
Hangianum(?)
2) uncertain status based on observations roots in limestone mix
Topperii
Charlesworthii
Esquirolei
3) those that do not grow roots in limestone mix
Rothshildianum
Jackii(???)
Anitum
Randsii
Well these are based on my observations on seedlings. Seems as if parvis are quite tolerant, the others are more questionable. Based on these observations I have decided to use more bark based mixes, my favourite has for many years been the pretty good mix of Lance Birk; 8parts bark, 2parts sheet moss and 1part sand.