Q A speaker I recently heard said he likes to use New Zealand sphagnum moss instead of bark for his orchids. What are the benefits of potting in moss?

A  Basically, there are three levels of moss quality. As often happens, the costs are commensurate with the quality. First there is the New Zealand sphagnum, which is the finest quality and most expensive. If you put it in a bucket with an equal dry volume of inferior mosses and wet fully, you can see from its much greater volume when wet why it is prized. Plus, it will outlast inferior mosses, although you must always repot more frequently with a moss medium, especially because most users apply inorganic fertilizers that hasten its breakdown. The next quality level of moss is the Tasmanian, followed by the Chilean product. Both are useful for orchid purposes with the provisos mentioned. North American and mainland Chinese sphagnum mosses are available for general horticultural purposes, but I cannot recommend these for orchid medium. —Andy Easton.