Fig. 22. Flake or French Spawn.
Virgin spawn is what we call natural spawn or wild spawn; that is, the spawn that occurs naturally in the fields, in manure piles, or elsewhere, and without any artificial aid. It is supposed to be produced directly from the mushroom spores, and is not a new growth of surviving parts of old spawn that may have lived over in the ground. It is far more vigorous than "made" spawn, and spawn makers always endeavor to get it to use in spawning the artificial spawn. It is seldom used for spawning mushroom beds because not easy to obtain. Now and again we come upon a lot of it in a manure pile; it looks like a netted mass of white strings traversing the manure. As soon as discovered secure all you can find, bring it indoors to a loft, shed, or room, and spread it out to dry; after drying it thoroughly keep it dry and preserve and use it as you would French spawn, for it is the best kind of flake spawn. In using virgin spawn for spawning beds I have obtained larger and heavier mushrooms than from "made" spawn, and the beds lasted longer in good bearing, but the weight of the whole crop has not been more than from artificial spawn.
How to Keep Spawn.—Spawn should be kept in a dry, airy place, somewhat dark, if convenient, and in a temperature between 35° and 65°. Wherever things will "must," as in a cellar, cupboard against a wall, or in a close, damp building, is a very poor place for keeping spawn. If the spawn is perfectly dry and kept in a dry, airy place, and not in large bulk, and covered, it will bear a high temperature with apparent impunity, but whenever dampness, even of the atmosphere, is coupled with heat, the mycelium begins to grow, and this, in the storeroom, is ruinous to the spawn. Judging from our natural mushroom crops, the spawn for which must be alive in the ground in winter, one concludes that frost should not be injurious to the artificial spawn, still my experience is that hard frost destroys the vitality of both brick and flake spawn. And this is one reason why I get our full supply of spawn in the fall and keep it myself rather than submit it to the mercy of the seed store.
New Versus Old Spawn.—How long spawn may be kept without its vitality becoming impaired is an unsettled question, but there is no doubt, if properly kept, it will remain good for several years. But I can not impress too strongly upon the reader the importance of using fresh spawn. Do not use any old spawn at any price; do not accept it gratis and ruin your prospect of success by using it. It takes three months from the time when the manure is gathered for the beds until the mushrooms are harvested. Can you, therefore, afford to spend this time, and undergo the care and trouble and expense, and court a failure by using old spawn? We have risks enough with new spawn, let alone old spawn. I do not use any more old spawn, but I have used it often and long enough to be convinced of its general worthlessness, unless preserved with the greatest care.
How to Distinguish Good from Poor Spawn.—This is a very difficult matter, notwithstanding what people may say to the contrary. If we could positively tell good from bad spawn, we would never use bad spawn, and, therefore, with ordinary care, have very few failures in mushroom-growing; for good spawn is the root of success in this business. Spawn differs very much in its appearance; sometimes the bricks show very little appearance of the presence of spawn, and still are perfectly good; and again, we may get bricks that are pretty well interlaced and clouded with bluish white mold or fine threads, and this, too, is good. When the bricks are freely pervaded with pronounced white threads this is no sign that the spawn is bad. Bricks dried as hard as a board may be perfectly good; so, too, may be those that are comparatively soft. Mushroom spawn should have a decided smell of mushrooms, and whatever cobweb-like mold may be apparent should be of a fresh bluish white color, and the fine threads clear white. Prominent yellowish threads or veins are a sign that the mycelium had started to grow and been killed. Distinct white mold patches on the surface of the bricks indicate the presence of some other fungous parasite on the mushroom mycelium; the absence of any mushroom smell in the spawn indicates its worthlessness and that the mycelium is dead. One familiar with mushroom spawn can tell with considerable certainty "very living" spawn and "very dead" spawn, but I am far from convinced that any one can decide unhesitatingly in the case of middling or weak spawn.
Mr. S. Henshaw, in Henderson's Handbook of Plants, tells us: "The quality of the spawn may be very easily detected by the mushroom-like smell, ... and I should have no hesitation in picking out good spawn in the dark." Sanguine, surely, but I have tried it and found the test wanting. M. Lachaume says that good spawn shows "an abundance of bluish-white filaments well fitted together, and giving off a strongly marked odor of mushrooms. All those portions which show traces of white or yellow mold or have a floury appearance, should be rejected and destroyed." Mr. Wright says: "A brick may be a mass of moldiness, and yet be quite worthless; and if the mold has a spotted appearance, as if fine white sand had been dredged on and through the mass, it is certain there is no mushroom-growing power there.... If thick threads pass through the mass and there are signs of miniature tubercles on them, then the spawn may be regarded as too far gone.... Clusters of white specks on the spawn denote sterility."
Mr. A. D. Cowan, of New York, who has the reputation of being an excellent judge of mushroom spawn, writes me: "To correctly judge the quality of brick spawn by its appearance requires experience in handling it, and a trained eye which enables one quickly to detect good from bad, fair to middling. As two lots seldom come exactly or nearly alike in appearance, it is hardly possible to give precise rules to follow, excepting the never-failing requisite which the spawn must possess to be good, namely, the moldy appearance on the surface, the more the better, without showing threads. Too many of these to a given space are a sure indication of exhausted vitality, arising generally from the bricks being heaped together when in process of manufacture, before they are sufficiently dried. Healthy bricks are usually of a dusty brown color, and of light weight. Black colored spawn is to be avoided, as a rule, and when the black appearance is very prevalent in a cargo of bricks it is a strong indication that the spawn has not run its course; and as it is not expected to do so after it has reached the hands of the retailer it is economy to cast it aside. Some persons break a brick into several pieces to see how it looks inside. To the experienced eye this is not necessary, or even to lay hands upon it, as the outward moldy appearance is the best of all evidence of its healthy vitality, and this never exists if the bricks have lost their germinating power, excepting, of course, where they have been kept damp, and the spawn has spent its power, which is detected by the white threads appearing in great quantity."
American-made Spawn.—So far as I have been able to find out by diligent inquiry, mushroom spawn is not made for sale in this country. But I am informed that a few growers do save and use their own flake spawn. Some of our principal growers, Van Siclen, Gardner, and Henshaw, for instance, in time past attempted to make their own spawn, but with only partial success, and now they confine themselves to the imported article. But this state of affairs can not long continue. The demand here for fresh mushrooms is so great, the industry of mushroom-growing so important, the price of imported spawn so high, and the quantity of foreign spawn imported annually into this country is so large, that, before long, we hope some one will find it to his advantage to make a specialty of growing mushroom spawn in this country to supply the American market. There is no practical operation in connection with the cultivation of mushrooms so little known or understood by the general grower as the growing (or "making," as it is commonly called) and preserving of mushroom spawn. General cultivators in England and France (outside of the Paris caves) do not make their own spawn; it is a distinct branch of the business, and carried on by specialists who grow mushrooms for sale in winter, and spawn in summer.
The time and attention required to produce a small quantity of first-class spawn are worth more than the cost of the spawn at the seed store. In order to make spawn profitably we must make it in large quantity, and we need not attempt to make it unless we have good materials and conditions for its proper preparation, and will give it every attention possible for its best development.