How deep the mold shall be put upon the bed is also an unsettled question. Some growers recommend three-fourths of an inch, others one, one and one-half, two, or two and one-half inches, and some of our best growers of fifty or seventy-five years ago were emphatic in asserting three inches as the proper depth, but among recent writers I do not find any who go beyond two and one-half inches. My own experience is in favor of a heavy covering, say one and one-half to two inches. In the case of a thin covering the mushrooms come up all right but their texture is not as solid as it is in the case of a heavy covering, nor do the beds continue as long in bearing; besides, "fogging off" is much more prevalent under thinly covered than under heavily covered beds; also, when the coating of loam is heavy a great many more of the "pinheads" develop into full sized mushrooms than in the case of thinly molded beds.
Opinions differ as to firming the soil. I am in favor of packing the soil quite firm, and have never seen good mushrooms that could not come through a well firmed casing of loam, and I never knew of an instance where firm casing stopped or checked the spreading of the mycelium or the development of the mushrooms. In the case of flat beds,—for instance, those made on shelves and floors,—a slightly compacted coating (and this is all Mr. J. G. Gardner uses) may be all right, but in the case of alongside-of-walls, ridge, and other rounded beds I much prefer and always use solidly compacted casings.
Mr. Henshaw has for several years used green sods about two inches thick, put all over the bed, grass side down, and beaten firmly. The advantage of using sods instead of soil, he thinks, is that the young clusters of mushrooms never damp or "fogg off" as they are apt to do when soil is used.
I have given this green sods method repeated and careful trials, and am satisfied that it has no advantages, in any way, over common fibrous loam; indeed, it is not as good. No matter how firmly a sod, having its green side down, may be beaten on to a bed of manure, there is barely any union between the two; the sod merely rests upon the dung, but so closely that the mycelium enters it freely. A slight movement or displacement of the sod after the spawn enters it will break the threads of mycelium between the manure and the sod, and this will destroy the immature mushrooms forming in the sod. This gave me a good deal of trouble. Stepping on the sod would disturb it. A clump of strong mushrooms formed under it sometimes displaces it in forcing their way to the surface.
Sods are only fit for use on flat beds where they can lie solid; on rounded or ridge beds they are too liable to be disturbed. And the trouble and expense of procuring sods are too great to warrant their use, even if they had any advantages.
CHAPTER XIV.
TOPDRESSING WITH LOAM.
In beds that are in full bearing or a little past their best we often find multitudes of very small or what we call "pinhead" mushrooms, that seem to be sitting right on the top of the loam, or clumps that have been raised a little above the surface by growing in bunches, or what we term "rocks"; now a topdressing of finely sifted fresh loam, about one-fourth to one-half inch thick, spread all over the bed, will help these mushrooms materially without doing any of them harm. But while this topdressing assists all mushrooms that are visible above ground, no matter how small they may be when the dressing is applied, I am not convinced that it induces greater fertility in the spawn, or, in other words, induces the spawn to spread further and produce more mushrooms than it would were no topdressing applied. I know that this is contrary to the opinions and writings of many, at the same time it is according to my own observation.
Go over the bed very carefully and pick out every soft or "fogged-off" mushroom, no matter how small it may be, and root out every bit of old mushroom stem or tough spongy material formed by it, and in this way get the bed thoroughly cleaned. Then fill up all the holes caused by pulling the mushrooms or rooting out the old stumps, and when the whole surface is level apply the topdressing evenly all over the face of the bed, avoiding, as much as possible, burying the well advanced mushrooms. While it would be very well to pack the dressing smoothly over the bed, it is impracticable; we may press it gently with the back of the hand on the bare spots between the mushrooms, but we should not even do this over the mushrooms, no matter how tiny they may be, else many of the "pinheads" will be injured and cause "fogging off."
But we can firm the dressing to the bed by watering it, which may be done over the whole surface of the bed, and without sparing the mushrooms, large or small. Use clear water and apply it gently through a water-pot rose. I always do this, and have never known it to injure the young mushrooms.