A  It sounds like you have been reading /Vanother of those British orchid books and an older one, at that. Loam is the technical term for good-quality garden soil, composed of nearly equal parts of sand, clay and humus. Very few garden books recommend the use of garden soil in pots these days. Any packaged potting soil for houseplants will do quite well for Bletilla striata. This is an easy-to-grow orchid that is often sold through seed catalogs. It will also naturalize fairly easily in many gardens where the ground does not freeze hard. In your garden, pick a spot that is shaded and receives dappled light, as for begonias. A rich and humus-y soil, like that recommended for camellias, will do them well, otherwise in a smallish pot, kept evenly moist. — Ned Nash