This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
I am not aware that the acknowledged authorities on this beautiful family of plants, who have favoured us with a revelation of the secrets of their art in the successful culture of the various species of Orchids, have ever spoken of stone as suitable material on which to place those which are generally recommended to be placed on blocks of wood. Neither have I any recollection of ever having seen Epiphytes with a stone to feed upon. This material may, however, be used beyond the range of my observation. Be this as it may, my present object is not to recommend stone blocks as the best sort that can be used, nor to say that I have, from any lengthened experience, found any advantage in using stone instead of wooden blocks, but simply to state that about a month ago I had to look about for a few suitable blocks for Orchids, and could not conveniently find them; and as is often the case in gardening, where a way cannot be found it has to be made, and so a few soft freestone blocks were hewn into shape something like small sugar-loaves, and placed a few inches deep in pans filled with soft water.
On one was placed a sickly plant of Phalsenopsis amabilis, and on others plants ofaerides Lobbii and A. Dayanum. The first named of these especially had not a fresh root, and just one leaf, when placed on the cone of stone. They were simply fixed in their places with a piece of matting, and a little fresh Sphagnum placed round their collars. The Phalasnopsis has now three fine healthy leaves of a dark-green colour, and is rooting and growing vigorously, and clinging to the stone with immense roots, which are covered with a gelatinous substance, the sign of health. The same may be said of the aerides.
The soft freestone, by capillary attraction, keeps itself always full of moisture, and it is, moreover, a good absorbent and conductor of heat; and, so far as my observation goes, it appears a material worthy the attention of Orchid-fanciers. Soft freestone can be cut into such a variety of shapes that a house of Orchids might be made to look much more picturesque than they are generally met with.
Drumlanrig Gardens. D. Thomson.