Why mushrooms are not plants, and why that matters for your growing

Most questions we get about a grow kit doing nothing come down to the same thing: people put it in the sun, water it like a plant and expect it to "grow" the way a plant does. That does not work, and the reason is not that you are doing something wrong, but that you are working with the wrong model. A mushroom is not a plant. On the tree of life it sits closer to you than to the tomato next to it on the windowsill. Knowing that makes growing suddenly logical.

1. A mushroom eats, it does not photosynthesise

A plant makes its own food from light, water and CO2. A fungus cannot. It secretes enzymes that digest wood, straw or coffee grounds outside its body, and absorbs the dissolved nutrients. So it eats, like an animal, only externally. What that means for your growing: the substrate is not the "soil" the mushroom stands in, it is its food. A grow block is a meal being slowly eaten, and when it is gone, it is gone. That is why every flush gets smaller, as we explained in an earlier piece.

2. It breathes in oxygen and breathes out CO2

Plants take in CO2 and give off oxygen. Fungi do exactly the opposite, just like us. A grow kit in a closed cupboard therefore literally suffocates on its own breath, and responds with long stems and tiny caps, see that story. Fresh air is to a mushroom what light is to a plant: not a luxury, a condition for life.

3. Light is a signal, not food

Because a fungus does not live on light, it does not need much of it. But it does use it: as a compass. Light tells the mushroom which way is "out", where to open its cap and release its spores. Hence the contradictory-sounding rule: no sun, but daylight. Anywhere you could read a book is enough. In full sun it dries out, in the dark it does not know where to go.

4. The mushroom is not the organism, the mycelium is

With a plant, what you see is the organism. With a fungus, what you see, the mushroom, is only the fruiting body: a temporary organ for spreading spores, comparable to an apple on a tree. The real organism is the mycelium, the white network running through the wood or substrate, sometimes living there for years. That is why you cannot write off a log that is "doing nothing" by looking at the outside, and why white fuzz on a grow kit does not mean something is wrong but that the organism is healthy. See is this normal.

5. It has no skin and no roots

A plant regulates its moisture with roots and a waxy layer on the leaf. A mushroom has neither. It absorbs moisture through its entire surface and loses it just as easily. That is why you mist a grow kit on the block and the air around it, not into a tray underneath, and why a dried-out log cannot be rescued with a watering can but can be with a night's soaking. And it is why a mushroom goes limp in the pan when wet and crisp when dry, see the washing story.

Why are fungi closer to animals?

Because they branched off from the same limb as the animals about a billion years ago, long after the plants had gone their own way. Fungi build their cell walls from chitin, the same material as a beetle's shell, not from cellulose like plants. They store energy as glycogen, like us, not as starch. And they eat, breathe and search. Once you know that, you stop seeing a grow kit as a plant in a pot and start seeing it as a slow animal living inside its food. That sounds odd, but it is the model that is right, and it is the model that stops you ever again putting a block next to the stove in the sun.

The practical summary

Feed it (substrate or fresh wood), let it breathe (fresh air), give it a compass (daylight, no sun), keep its skin moist (misting, soaking) and judge the organism, not the fruiting body. Five rules, all traceable to the fact that a mushroom is not a plant. Know them and you hardly need to read the rest of this blog. Though you are welcome to, of course.