Shiitake, bark first

A white block does not get opened. The bark, two to four weeks later, and then cold water, are the start of the harvest.

White is not the moment

Shiitake is Lentinula edodes, a decomposer of hardwoods. The path to the block resembles an oyster’s only at the start: liquid culture into sterilised grain, white grain crumbled into wood, the bag kept shut, no openings out of curiosity. Then the clocks diverge. An oyster, once the block is white, wants a cut within a few days. A shiitake, once the block is white, is not ready. It has occupied the food. It has not yet built the skin the mushrooms will come from.

That skin is the bark. It forms inside the bag, after no bare substrate is left, and it usually asks for two to four weeks. In those weeks the surface, seen through the plastic, stops being an even white. Bumps appear, like popcorn, then a light brown, then a deeper brown, leather, in patches that join up. The block gets firmer. The smell stays of mushroom, sometimes stronger, never acid. Anyone who takes the plastic off the day the last bit of sawdust disappears under the white is opening a mycelium that does not yet have its defence. The two-to-four-week calendar is an order of magnitude. The real signal is the bark. If at four weeks the block is still almost entirely white, you wait. If at two weeks it is already brown and bumpy over nearly the whole face, the calendar has lost and the bark has won.

Colonisation, before any of this, is comfortable around 20–24 °C. Colder, and the white takes an extra month, with the bag exposed. Hotter, toward 28 °C, and bacteria, if the wood was too wet, win before the mycelium. This is not a species for results in ten days. Grain can ask for three weeks. A block as many again, and then the bark. Throwing out a white, clean bag because “it is not making mushrooms” is the mistake of someone timing a shiitake on an oyster’s clock.

What the bark is doing

The bark is not a decorative delay. It is a tissue. The surface mycelium oxidises, packs itself, and forms a rind that holds water and resists the spores circulating in a kitchen better than naked white does. Pins, later, are born from that rind, not from sawdust that has only just been covered. The bumps under the plastic frighten anyone who sees them the first time: they look like a bag deforming, or a contamination in relief. If they stay in the colours of the bark, from white to brown, and the smell is clean, they are the rind organising itself. You do not open the bag to scratch them.

A little amber or brown liquid, pressed against the plastic during these weeks, is common. Those are metabolites. You tolerate them. A slimy lake, a smell of acid, a zone that collapses and smells of sweet rot: that is bacteria, and the bag does not get washed. Powdery green, if it appears, is almost always Trichoderma, and it appears much more willingly on a white you have stripped than on a bark left in peace. The plastic, in this period, is part of the method. It is not packaging you forgot to remove.

Some strains brown in two weeks. Others ask for more than four, especially if the block is large or the room is cold. Forcing the opening to make the sums work is how you get a block that goes green in four days and no mushrooms. Patience here is not a moral trait. It is the chemical time of a rind.

What happens if you open a white block

Taking the plastic off a block that is still white does three kinds of damage at once. Naked mycelium loses water quickly and the surface crusts in a sterile way, without becoming real bark. Mould spores, which find little purchase on a brown rind, find open food on that white. And the few pins that sometimes come out anyway are weak, they abort, and they leave wounds. The block then splits or covers itself in green. At that point there is no second gesture that takes it back. You bag it and discard it, without opening it further in the kitchen.

The same is true of a water shock done too early. Submerging a white block means flooding a mycelium that has no rind: water fills the spaces, the internal air disappears, the centre rots. The shock is a tool of the bark, not of the white. If you have already removed the plastic and the block is still pale, the only honest move is to keep it humid, out of a draught, and hope it browns anyway. Sometimes one face manages it. Often it does not. The guide exists so you do not arrive there.

An oyster-style side slit, cut into the white “just to try,” is the same opening under another name. Shiitake does not fruit from a side slit on a bag that is still pale. It wants the rind, then air over the whole surface, or over most of it.

The cold water

When the bark is there, you remove the plastic. The naked block goes somewhere cool, with indirect light, high humidity and air that changes without hitting it. If it is still heavy with water, the first flush sometimes starts from that passage alone: bark, new air, a little cool. Give it a week. If the pins do not appear, then the shock.

The shock is a soak in cold water for several hours. An honest interval is between four and twelve hours, not a weekend in the bucket. The block floats: it needs to be held under, with a clean weight, so the whole rind gets wet. The water does two jobs. It rehydrates a bark that had dried at the surface. And the jump in temperature is a fruiting signal, not a punishment. Then you drain it properly, until it no longer drips, and you set it on a rack, not in a puddle. The pins, if the room is not hot and the air is not dry, come in the following days, as dark buttons on the rind.

Mist the air, not the buttons. Water sitting on a young cap blotches and invites bacteria. A radiator draught turns them papery. Fruiting shiitake prefers the cool: the thick form wants the low end of the range. A naked block in a kitchen at 25 °C may throw thin mushrooms or none, and the rind stays a target for green if it also stays wet.

Between flushes it has to dry back

Here shiitake separates from oyster in a sharp way. An oyster, between harvests, wants to stay humid. A shiitake wants a period in which the block dries, lightens a little and firms up again. One or two weeks, sometimes more, in air that is not desert-dry but also not a dripping tent. A rind kept soaking the whole time is a rind that goes green. Green on the bark, after the first flush, is often this: too much water, for too long, without the rest.

When the block is lighter again and the rind is dry to the touch, but not cracked until it flakes, you repeat the cold bath. Then the rack, humidity, air. Later flushes arrive this way, for weeks or for months, as long as food remains in the wood and the rind is not rotten. How many there are is not something you sign. A well-barked block can give several. A block opened while white often gives none. When the smell turns acid, or the green occupies a face, the series is over. You do not brush the green off hoping to save the rest: the spores are already there.

Harvest when the veil under the cap is just tearing and the cap is still slightly closed, before it becomes a plate and dumps a white dust. That dust is spores. It makes a mess, and the mushroom is already past its best. The whole body, with a clean cut at the base, leaving no stump to rot on the rind. Paper in the fridge, a few days.

Donko and Koushu

Donko and Koushu are not two ways of cutting the same mushroom. They are two tendencies of the strain, and the room decides how much of that tendency you see.

Donko is the form with a thick cap, often split at the surface like a loaf, the flower that cultivation looks for in the cool. The split has a mechanism. The skin of the cap sets, and the interior keeps growing, so the surface opens into a pale network. It happens when the fruit goes slowly, in a cool room, toward the bottom of the range, around 12–16 °C, with humid air and no drops on the cap. Misting the cap fills the cracks and blotches them. A Donko in the heat, above 18–20 °C, can still fruit, but the caps stay smoother and thinner. You have a shiitake. You do not have the form that strain was kept for. The cool is not replaced by a longer soak. The soak starts it. The room shapes it.

Koushu is the opposite tendency: faster from the shock to an open cap, less thick in the flesh, less dependent on a room that stays cold. It still fruits willingly when the air sits around 17–20 °C, where a Donko would already have given up on cracks. It does not become a flower because you moved it to a cellar for two days. It may thicken a little. The speed and the simpler cap stay in the strain. It makes sense when your room will not hold 14 °C, and you would rather have a mushroom that arrives at an honest form than a smooth, disappointed Donko.

Choosing one or the other before you have a place is the real decision. A cold, patient place rewards Donko. A place that is only cool, and a shorter calendar, rewards Koushu. Neither rewards a block opened while white.

The Donko shiitake liquid culture is the seed of the thick form. The crack on the cap is made by the cold room, not by the label alone.

Coltura Liquida Shiitake Donko 10ml Micelio Lentinula Edodes Funghi€9,42

The Koushu shiitake liquid culture is the seed of the faster form. You do not ask it for the flower.

Coltura Liquida Shiitake Koushu 10ml Micelio Vivo Funghi Gourmet Materiale Micologia Le…€11,00

Wood, not straw

Shiitake eats hardwood. Pasteurised straw, which an oyster occupies in a week, does not carry this cycle: it lacks the density, it lacks the duration, and pasteurisation is not sterilisation. A straw block does not make shiitake bark. It makes mould, or a poor white. Sterilised beech is the food of the species. Colonised grain goes into it at a generous proportion, closer to one in five than one in ten, because a slow mycelium on naked wood loses weeks and sometimes the whole game.

A syringe straight into the bag of sawdust, without grain, is too dilute. Ten millilitres is inoculum for more than one bag of grain, not a substitute for the grain. Then the grain, white and right-smelling, seeds the wood. You label the strain, Donko or Koushu, and the date, because during the bark weeks the bags all look alike.

Sterilised beech is that wood. Use it while it is still what it claims to be. A filter that is months old has already let air in.

Substrato Funghi Faggio Sterilizzato — 1 kg / 2 kg€12,90

Shiitake occupies months, not a weekend. While one block is in its bark, the next sterile wood is what you need if you want the cycle not to stop. The prepaid hardwood sequence is that sequence, over three, six or twelve months. It does not shorten the bark, it does not replace the shock, and it does not choose the strain for you. It only keeps you from reaching white grain and having no still-sterile wood in the house.

What this guide is not

It is not a number of flushes and it is not a recipe. It is the reason a white block is left closed, and why the cold water comes after the rind, not before. If you opened early and the green arrived, the lesson has already happened: the bark weighs more than the hurry.