One of the biggest puzzles about mushroom growing is the requirements of your favorite fungi when it comes to light. Mushrooms are known for being found in dark, damp places, but they are also very plant-like, and plants need light.
The reality of mushrooms is that they do not need darkness to grow, though they are known to grow faster in the dark than they do in the light. Mushrooms are 92% water and so thrive in moist humid conditions. The darkness usually retains moisture and humidity that may have been burned away by the direct sunlight or water extracted from the mushrooms due to the dryer conditions during the day.
This should not be mistaken for saying that mushrooms will grow better with no light. Some light is important for the fruiting process—the part that actually produces mushrooms—as light is one of the ways in which a mushroom detects that it has reached an appropriate area for fruiting. Naturally, there is a lot to this subject, and we’d like to cover more of it for you. So keep reading, and we’ll do just that!
What Triggers Mushroom Fruiting?
Mushroom fruiting is triggered by a range of different factors that need to happen at certain stages of the mushroom’s development. The precise details of these factors can differ depending on the species of mushroom, but the general shape of events remains the same.
The mycelium — which is the root-like structure (the largest part by volume) that the mushrooms sprout from—will typically strive to colonize as much of its available environment as it can. In an artificial setting, the boundaries of this environment could be something like the edge of a pot, or plastic bag, though, in nature, there are natural boundaries that can trigger the mycelium to be ready for fruiting.
Fruiting, of course, is the process by which the mycelium sprouts the mushrooms that we know and love. As mycelium grows through the substrate—often soil—it is mostly underground. As such, one of the factors that lead to fruiting is the level of carbon dioxide in around the mycelium. When the carbon dioxide levels drop, the mycelium sees that as a sign that it has reached the surface of whatever substrate it is growing in, which in turn means it is has found an area where it can fruit and reasonably expect its spores to find fertile ground to take hold.
The next set of factors are the ones that can differ quite significantly from species of mushroom to species of mushroom. The humidity, temperature, and light levels all play a role in the mushroom fruiting, but the amount of each that is required is not always the same. Some mushrooms prefer more humidity than others; some prefer colder temperatures than others. If you are attempting to grow mushrooms artificially, you will need to know the ideal conditions for the specific species you are growing.
What Conditions do Mushrooms Need to Grow?
The exact amounts of things like light and temperature may differ from species to species, but all mushrooms typically need the same set of conditions in order to achieve healthy growth. Let’s take a look at those conditions in a little more detail;
Like animals, fungi synthesize the nutrients it needs from organic material. This often comes in the form of fertile soil, but the substrate can also be living trees, dead animals, and a range of other things that contain what they need. In particular, the mushrooms are looking for the following things;
The amounts of these ingredients are what determines the best substrate for any given mushroom. For example, compost is often the best choice for growing the ever-popular button mushroom, whereas something like shiitake prefers a substrate like wood.
It doesn’t take an expert to know that mushrooms thrive in moist conditions. Water can be found at the root of all life on Earth, and mushrooms, in particular, need plenty of it for healthy growth. This is an important factor if you are growing a mushroom that prefers wood, as a dried log will need to be hydrated before your mushrooms can take hold. Of course, this is not a problem for living wood. Compost with a good mixture of ingredients should remain moist without any assistance, but watering is always an option.
Despite being often mistaken for a type of plant, mushrooms are very much their own form of life, and one of the most significant differences between fungi and plant life is the fact that, unlike plants, fungi cannot convert sunlight into energy. This means that light is not an essential factor in mushroom growth, as it would be with a plant. That being said, light does play a role in the growing process, and many growers find that a roughly natural day/night cycle is best for good growth. Still, mushrooms should be kept out of direct sunlight, which has a tendency to dry things out. And, as we’ve already mentioned, moisture is crucial for a healthy mushroom.
Temperature is perhaps the most variable of the factors that go into growing mushrooms since different species can require significantly different temperature ranges. For example, button mushrooms typically prefer temperatures in the high fifties (Fahrenheit), while shiitake are more in the mid-seventies range. You would be able to grow both mushrooms in the same growing environment, but you may find yourself in a situation where neither mushroom is getting their ideal temperature, which defeats the object somewhat. If you’re going to grow mushrooms in an artificial environment, you may as well take advantage of that control to provide them with the perfect conditions.
Do All Types of Mushrooms Grow in the Dark?
As mentioned above, mushrooms do not extract energy from sunlight in the way that plants do, so they do not need sunlight to grow.
That being said, light does have a role to play in the fruiting process. Light, albeit dim light, is often needed for mushrooms to fruit, as it is one of the ways they determine that they are in a good position to do so.
The natural habitat of mushrooms is the moist, lower regions of forests, shaded by the canopy of trees. Here, the mushroom would get at least a few hours of reduced sunlight a day, and that is what you should strive for in your growing space.
As an interesting aside, many growers will observe that their mushrooms often grow faster in the dark. One thing to bear in mind is that the light you cast on your mushrooms should not be full sunlight. Not only might this dissuade your mushrooms from fruiting, but it will also dry out some of the moisture in your growing space, which reduces the effectiveness of that space.
Indirect sunlight can be an excellent tool for growing mushrooms since it is essentially on a natural timer that mushrooms have evolved to grow under; just be sure that it is indirect sunlight.
A dim growing lamp should also do the trick, however.
What Light is Best for Growing Mushrooms?
As a general rule, you can’t beat sunlight for growing mushrooms. Though, as we mentioned above, you do not want your mushrooms to be in direct sunlight as that will dry them out. It is sunlight that mushrooms evolved with, and in terms of expense and ease of use, it doesn’t get much better than the big natural light in the sky. Not to mention you don’t need to worry about setting timers.
Still, not every growing space can make use of sunlight, especially if it is underground. If you are going down the artificial lighting route, there are a few things to consider.
Firstly – a low-heat output light, like an LED, is preferable, as high-heat lighting can interfere with the growing conditions of your space.
Secondly – you want to get an even dispersion of light throughout your growing area, or you risk having some mushrooms fruiting and others not, making for inefficient use of your space.
The next thing you need is a way to have your lights turn on and off to a schedule. Granted, you could do this yourself manually, but given the inexpensiveness of timer controllers, it would make far more sense to set this up to be automatic.
In terms of the rate of growth at any given time, mushrooms do indeed grow better in the dark in the sense that they tend to grow faster in the dark than they do in the light. This is not to say that light plays no role in a mushroom’s lifecycle, even if mushrooms do not absorb sunlight the same way that plants do.
There are undoubtedly steps that can be taken to maximize the efficiency of the mushroom growing process, but for most home growers and enthusiasts, the best option is a certain amount of natural sunlight. By setting your growing space up somewhere it can receive indirect natural light, you are giving your mushrooms what they have been designed to receive and have been for possibly eons. Just be sure to avoid having your growing space in direct sunlight, or you risk the mushrooms not fruiting and the growing space getting dried out.