Mushroom Growing in the Paris Caves.
In caves and subterranean passages
underneath the city of Paris and its environs, thousands
of tons of mushrooms are artificially produced every
year. These underground caves and tunnels are
abandoned quarries from which white building stone
and plaster have been excavated, and as the veins
of stone permeated through the bowels of the earth,
40 to 125 feet deep, so were they quarried, and the
blocks brought to the surface through vertical shafts.
It is these tunnels, varying in height and width as
the veins of stone varied, that are now used for mushroom-growing.
M. Lachaume, in his book, The Cave Mushroom,
tells us: “In the Department of the Seine
there are 3000 quarries; those which have been abandoned
and which are situated close to Paris at Montrouge,
Bagneux, Vaugirard, Mery, Chatillon, Vitry, Honilles,
and St. Denis, are used by the 250 mushroom-growers
of the Department. There are several of these
quarries with horizontal galleries driven into the
calcareous rock from the level of the road, which
are mostly large enough to accommodate a good sized
cart, but the majority can only be entered, like many
coal mines, by vertical shafts 100 to 125 feet deep,
down which everything has to pass. The laborers
climb up and down a ladder, and the fresh manure is
shoveled down the shaft from above, the waste stuff
and mushrooms being hauled up in baskets from beneath
by means of a windlass.”
The manure used is obtained from the
Paris stables and furnished by contractors, with whom
the mushroom growers make special bargains because
they are very particular about the kind and quality
of the manure they use. Some of these growers
use as much as 2000 to 3500 tons of manure each a
year for their mushroom beds. To the caves in
the immediate neighborhood of Paris the manure is
hauled out in carts, but to Mery and other places
too far distant to be within easy carting distance
it is sent by rail. The mushroom growers consider
that the manure from animals that are worked hard
and abundantly fed on dry, good food is the best;
the droppings from these are always dry and rich in
ammonia, nitrogen and phosphates. The manure from
entire horses that are worked hard they regard as
the best, and, next in value, that from mules.
The manure from horses kept for pleasure, such as carriage
and riding horses, is regarded as poor, notwithstanding
the high feeding of these animals, and the manure
from horses fed on grass or roots, also that of cows,
as worthless. Stress is laid on the importance
of having a good deal of urine-soaked straw in the
manure, and this is another reason why manure from
draught horses is preferred to that from animals kept
for pleasure, as the bedding of the former is not apt
to be kept so clean as that in aristocratic stables.
The preparation of the manure is conducted
near the mouth of the caves or shafts on a level,
dry piece of ground, and altogether out of doors.
As soon as sufficient manure for a pile is obtained
it is forked over, thoroughly shaken up and intermixed,
divested of all extraneous matter such as sticks,
stones, bottles, scrap iron, old shoes, and the like
we find in city stable manure, and any dry straw is
moistened with water. It is then squared off
into a heap forty inches high and trodden down to
thirty inches high. In this state it is left for
about six days, when it is turned, shaken up loosely,
the outside turned to the inside, and all dry parts
watered; the same shallow square form is retained,
and it is again trodden down firm. In about six
days more it is again turned, shaken up, watered,
squared off, and trodden as before. In about three
days after this it should be fit for use and may be
turned, shaken up loosely, and dumped down the shaft
into the cave and carried to the spot where the beds
are to be formed. Of course these operations must
be modified according to circumstances and the condition
of the manure.
In making the beds the ground is first
marked off. The first bed is made alongside of
the wall, and rounded to the front; the other beds
run parallel with this and may be straight, crooked,
or wavy, as the interior of the cave may suggest.
The beds are all ridge-shaped, eighteen to twenty
inches wide at the base, eighteen to twenty inches
high in the middle, six inches wide at top, and the
sides sloping. Pathways twelve inches wide run
between the beds. The workmen build the beds
by piece-work and receive one-half cent per running
foot. A good workman can make 240 feet a day
(Lachaume). The beds are built neatly
and firmly and with much nicety as regards size and
proportions. But the workmen do not use a fork
or any other tool in the construction of the beds;
they lift, shake up, spread and build the manure with
their naked hands and pack it firm with their knees.
The spawn is obtained from the working
beds and is what the mushroom growers there call “virgin”
spawn, though not at all what we know by that term.
As a succession of beds is kept up all the year round
it is an easy matter for the growers to get their
spawn at any time. The best time to get the spawn
is when the young mushrooms are first appearing.
A bed or part of a bed in capital working order is
selected and broken up and the cakes of manure thoroughly
matted up with the active mycelium are selected for
spawning the fresh beds. It is asserted that from
this active spawn crops of mushrooms appear in twenty
days’ less time than if dry spawn were used.
The French spawn is used. Somewhere
between the seventh and fourteenth day after making
the bed it will be in condition for spawning.
Break the spawn into pieces between two and three
inches long, two inches wide, and three-fourths of
an inch thick, and insert these pieces in two rows
along the sides of the ridges; the first row eight
inches above the ground, the second row eight inches
above the first, and the pieces put in quincunx fashion
eight inches apart in the row. The manure is firmly
packed in upon the spawn, the surface left smooth and
even and without being further disturbed until earthing
time.
Much stress is laid upon stratifying
the spawn before using, when dry spawn is employed.
About eight days before a bed is to be spawned the
dry spawn is spread out in a row on the floor of the
cave or cellar so that it may absorb moisture and
the mycelium begin to run. At spawning time these
cakes or flakes are broken up and used in the ordinary
way, and, it is claimed, with a week’s difference
in favor of the early appearing of the mushrooms.
But no more spawn than is necessary for immediate
use should be stratified, for it will not bear being
dried and damped again.
The chips and powder of the stone
which has been taken out of the quarry and which can
be had in abundance on the floor of the quarry or on
the surface of the ground around the shaft, are sifted,
and the finer part saved and mixed with earth in the
proportion of three parts of stone dust to one of
earth, and with this the beds are molded over.
The powdered stone is strongly impregnated with salts,
so advantageous to the mushrooms.
In seven to nine days after spawning,
the beds are ready for earthing over. This depends
upon the condition of the spawn and how well it has
run in the manure. Before being earthed over the
outside surface of the beds should be covered with
white filaments radiating in all directions which
give to the beds a bluish appearance. When the
bed is in the proper state for being covered with
earth the mold is laid on equally and firmly over
the surface about three-fourths of an inch deep.
It is then thoroughly watered through a fine-rosed
watering pot and allowed to settle until the next
day, when it is beaten solid by the back of a wooden
shovel. The bed now needs no further care until
the young mushrooms appear, except a light occasional
watering should it get dry.
In spacious, high-roofed caves the
mean temperature is about 52 deg. F., while
in narrow, low-roofed ones it is about 68 deg..
Of course this makes a wide difference in the time
of bearing and duration of the beds made in the different
caves; those in the warm caves come into bearing sooner
and stop bearing quicker than do those in the high-roofed
caves. On an average the first mushrooms appear
in about forty days after the beds are spawned, and
the beds continue bearing for forty or sixty days,
but toward the end of that time the yield diminishes
very rapidly.
They are gathered once a day, usually
about midnight, so that they may reach the Paris market
early in the morning. In size the mushrooms range
from three-fourths to one and five-eighths inches in
diameter of top, and are pure white in color.
The workmen always gather the mushrooms by plucking
them out by the roots, and never by cutting them; the
gatherers have two baskets, carried knapsack fashion
on their back; one is to receive the mushrooms as
they are picked, the other contains mold with which
to fill in the little holes made by pulling the mushrooms
out of the bed. In some caves one man gathers
the mushrooms and leaves them in little piles on the
bed as he goes along, a woman comes after him and
places them in a basket, and a man follows her and
fills up the holes with earth. Before bringing
the mushrooms up out of the caves they are covered
over with a cloth to avoid contact with the outer air,
which is apt to turn them brown. They are then
placed in baskets that contain twenty-three to twenty-five
pounds and sent to market, where they are sold at
auction as they arrive. Or they may be sent to
preserved-vegetable manufacturers, who contract for
them at an all round price.
Proper ventilation is regarded as
being of great importance, not only for the sake of
the workmen, but also for the mushrooms, which will
not thrive in an impure atmosphere. Ventilation
is afforded by means of narrow shafts surmounted by
tall wooden chimneys whose upper ends are cut at an
angle so that the beveled side faces north. In
order to avoid sudden changes of temperature and strong
draughts, fires, trap doors, and other means employed
in assisting the ventilation of coal mines are adopted.
To stop strong draughts, too, in the passages, tall,
straw-thatched hurdles are set up. In narrow caves
the breath of the workmen, the gases given off by
fermentation, and the products of combustion of the
lamps would soon so vitiate the atmosphere as to render
the caves uninhabitable were they not properly ventilated.
Indeed, it frequently occurs that caves in which mushrooms
have been grown continuously for some years have to
be abandoned for a year or two because the crop has
ceased to prosper in them. But after they have
been thoroughly cleared of all beds and the surface
soil that would have been likely to be touched or
affected by the manure, and ventilated and rested
for a year or two, mushrooms can again be grown in
them successfully.