The French often cultivate mushrooms in cellars as well as in the caves described in the [next chapter]. Preference should be given to a dry warm cellar; it should be as dark as possible, and exposed to no draughts. Beds can be made in cellars in many ways. Those made in the middle should always be formed with two sides, while those against the walls should only be half as thick, on account of their having only one useful side. It is also possible to arrange them on shelves, one above the other. For this purpose strong bars of iron are driven into the walls, upon which are placed shelves of the proper size covered with earth, upon which is formed a bed, that is treated exactly as those made upon the ground. These beds are just as productive as any of the other kinds. They may even be made on the bottoms of casks, which should be at least two feet six in diameter; and they are built up in the shape of a sugarloaf, about three feet in height, and the pieces of spawn are placed an inch and a quarter deep, and sixteen inches apart. A barrel is sawn crossways into two pieces, each forming a tub. Holes are made in the bottom of each, and a thin layer of good soil is spread over them inside. They are then filled with good well-prepared stable manure, just like that used in the case of ordinary mushroom-beds, the different layers of dung in each tub being well pressed down. When the tub is half full, six or seven good pieces of spawn are placed on the surface, and the remainder is piled up with manure, which is well pressed down, the operation being completed by giving to the heap the form of a dome. The tubs thus prepared are placed in a perfectly dark part of a cellar, and eight or ten days afterwards the dung is taken up until the spawn is visible, in order to see whether it has commenced to vegetate and develop little filaments. If the spawn has spread, the surface must be covered with soil, care being taken to use only that which is fresh and properly prepared. In this or any like way there should be no difficulty in growing mushrooms: the boxes or tubs could be filled anywhere, and then carried into the spare cellars, &c. In this way objections against steaming manure might in many cases be got over.
Among the many and various structures in which mushrooms may be grown, but which we rarely see utilized for that purpose, may be mentioned all kinds of greenhouses, stoves, pits, and frames. Some of the best crops I have ever seen were in cold greenhouses almost too ruinous to grow anything else. In mid-winter the floors of all houses in which a genial temperature is kept up for forcing or other purposes, offer excellent positions for producing mushrooms quickly and abundantly. Small ridge-like beds might be made on the floor of these, and, with the genial temperature usually kept up in such places, would probably come into bearing a month or so after being spawned. How often, for example, do we notice the floors of large vineries, in mid-winter or very early spring, quite bare, especially after the vines are started. Now just at that season the genial heat that would be given off from the slightly fermenting materials used for the mushroom-bed is that which would be most congenial to the tender breaking vines, and with a little attention in this way a first-rate crop of mushrooms could always be gathered from the early vinery, and in houses where no artificial heat was applied they could also be grown abundantly. A covering of hay would, however, be necessary in cold houses in mid-winter, to prevent excessive variation of the temperature, and also in spring and summer to prevent excessive drying or scorching of the beds by a hot sun. I have even seen excellent crops grown on the floor in an old lean-to house, the beds covered with a foot or so of hay, occasionally sprinkled with water to prevent excessive heat on the surface of the bed. In small places where every foot of space in the glass-house is likely to be occupied with plants, it is not easy to carry out the foregoing suggestions, but even if a small early vinery were occupied with plants, it would be desirable and practicable to introduce a series of rough boxes devoted to mushroom culture.
Apart from empty greenhouses altogether, the space beneath the stages in numbers of glass-houses of every type may be utilized for the production of mushrooms. These positions are usually unoccupied, occasionally they are used for storing fuchsias, &c. in winter, but very seldom are they turned to so good account as they might be in the way I recommend. The stage in the small greenhouse is frequently elevated so that there is plenty of room to get beneath it: if at the back or end there is no way of walking readily under the stage, an opening should be made. The only difficulty that could possibly occur would arise from the drip from the plants on the stage above. This, however, can be easily guarded against by spreading a piece of tarpaulin or oil-canvas over the bed or beds. With beds properly made, a coat of dry hay or litter, and a piece of tarpaulin, every owner of anything in the shape of a greenhouse with a stage in it may grow mushrooms throughout the autumn, winter, and spring months, and even in summer by keeping the surface of the hay or litter moist. Of course, if there be room for but one bed, a succession cannot be kept up, and in this case a bed should be made in autumn, which, if well managed, should be in full bearing for a month or six weeks before and after Christmas. There are, however, numerous spaces such as those alluded to where there is room to make a succession of beds. No person having but one greenhouse need fear much or any inconvenience from the odour of the manure—at least, not after the beds are earthed. The couple of inches of soil over the manure would absorb any vapour given off by the bed.
Wherever the cultivation of cucumbers or melons in pits or frames is carried out, nothing can be easier than to grow large crops of mushrooms after the melons, &c. are cleared away. The spawn may be inserted over the surface of the little mounds usually made for the reception of the young melon plants, and also over the remaining surface of the beds which are generally covered with a few inches of earth. After the melons have done bearing and the haulm is cleared away, the spawn will usually be found to have spread through the deep mass of earth in the beds. As little or no water is given or required while the melons are ripening, a good soaking of tepid water will generally be necessary to encourage the mushrooms to start into profuse bearing. If the season and situation be mild and warm, the lights may be taken off; and if the sun be very strong, the beds may be shaded with canvas or mats. If the season be late and cold it will, on the other hand, be desirable to keep on the lights, and even to cover them in cold weather.