A similar thing happens with many cacti in Mexico. They are found only in limestone outcrops - not even 1 foot outside them. This lead many cactophiles to add limestone to their potting mix. However the real story is somewhat different. Indeed the pH of the soil is made more alkaline by the limestone but this is nearly all leached by rain and the actual pH of the growing area is closer to neutral. This and the acidic soil of N. calcicola just goes to show how you need to take the total surrounding environment into account when looking at mixes to use in cultivation - this includes makeup of the soil substrate, rain amount and frequency, how well rain leaches into the soil and how quickly it drains away, the ambient temperature, the ground temperature, what nutrients are available (minerals humus etc), and anything else you can think of. Add this all up and you will find that you will settle on a fairly standard mix for a large range of your plants be they bulbous, perennials or annuals. The plants will adapt to your conditions - remember they are not in habitat. Obviously this is not meant to be a blanket statement, there are exceptions where you need to provide special conditions. Wayne Robinson "Any sufficiently advanced technology is indistinguishable from magic." --Arthur C. Clarke Here's to us magicians!