Mushroom Grow Light: Is It Necessary? 

Mushrooms, a fascinating and diverse kingdom of organisms, often conjure images of damp, dark forests. This association leads to a common question among mushroom cultivators and enthusiasts: Do mushrooms need light to grow? 

Unlike plants, mushrooms do not rely on photosynthesis, so light is no longer an energy source for them. Does this mean they can grow safe and sound without light? This blog will delve into the nuances of light's role in mushroom growth. Let’s go!

Do Mushrooms Need Sunlight

The short answer is no. Mushrooms can grow in complete darkness. Why? Mushrooms belong to the fungi kingdom, which sets them apart from plants. One of the key differences lies in their nutritional processes. 

Unlike the plants we know, mushrooms lack chlorophyll, the green pigment essential for photosynthesis – the process by which plants convert light energy into chemical energy. Consequently, mushrooms do not depend on light for their nutritional needs. How do mushrooms get energy, though? They absorb nutrients from their surrounding environment, often decomposing organic matter like dead plants, wood, leaves, or animals. 

However, if there’s sunlight, will it help mushrooms to grow better? 

What Does Light Do to Mushrooms

Direction of growth 

To start with, light is simply used as a directional cue. This phenomenon, known as phototropism, involves the mushroom growing towards a light source. While not as pronounced as in plants, this directional growth helps the mushroom expose its spore-bearing surfaces optimally for spore dispersal.

When growing mushrooms indoors, providing some light can help them grow more upright and uniformly, so your mushrooms can look neater and better shaped. And it can be any kind of light, even a torch can do the trick.

Interestingly, mushrooms also exhibit gravitropism. They can sense gravity and adjust their growth accordingly. This means that even in complete darkness, mushrooms can still orient themselves correctly, with caps growing upward and stems downward.

Growth-Promoting Effects of Blue Light

Based on research on the blue-light and red-light response of the oyster mushroom, blue light significantly increases the fresh weight and size of the pileus (cap) and stipe (stem) compared to red light and dark conditions. 

In the pileus, blue light upregulates genes involved in glycolysis and the pentose phosphate pathway, which are essential for generating energy (ATP) and biosynthetic precursors in non-photosynthetic organisms like mushrooms.

Indeed, mushrooms do not use light for energy, but blue light does act as a signal to activate metabolic and developmental pathways.

Fruit Set Stimulation

For many fungi, light acts as a trigger that initiates the formation of mushrooms from the underlying mycelium, a process called fruiting. For example, oyster mushrooms (Pleurotus spp.) typically require light exposure to start producing sporophores (fruiting bodies).

This light can be natural or artificial, as long as it’s in a suitable spectrum: white light or blue light(430–470 nanometers) both work well. Without this light cue, some species may never fruit, even if all other conditions (humidity, temperature, substrate) are perfect.

Do You Need a Mushroom Grow Light

Strictly speaking, no. You don’t need a grow light to cultivate mushrooms, even indoors. However, as mentioned above, light does offer certain benefits in mushroom cultivation.

So, while optional, using a blue-spectrum grow light is still recommended if you want healthier, more productive, and better-shaped mushrooms. If you’re looking for a light that truly benefits mushrooms, the Mars Hydro ADlite Blue 30 is an ideal choice.

Emits pure 440nm blue light, the most effective wavelength for mushroom development. Meanwhile, it’s not a full-spectrum grow light, so it contains no red light, which has been shown to inhibit fruiting body growth in some species. With its help, you can expect compact, sturdy caps and vigorous stems.

Not sure if you should invest or not? Maybe check out what the expert says.

FAQs about Mushrooms and the Light

Do mushrooms grow better in light or dark?

Mushrooms can grow in both light and dark conditions. However, exposure to blue light (around 430–470 nm) has been shown to enhance growth, especially in the cap (pileus), and can improve shape and yield. So while they don't need light to survive, they often grow better with it.

Can you grow mushrooms with LED lights?

Yes, but it’s not a must. LED lights are ideal for growing mushrooms indoors. They’re energy-efficient, low-heat, and many models provide the blue light spectrum that benefits mushroom development. 

How much light do mushrooms need to grow?

Mushrooms need only a small amount of light. Typically, 6-8 hours per day is sufficient. The light doesn’t need to be intense, as it’s mainly a signal, not an energy source. Even a basic LED bulb or low-intensity grow light can do the job.

Do mushroom grow bags need light?

Not during colonization. Mushroom grow bags should be kept in the dark while the mycelium is spreading. Once the primordia (pins) begin to form, light plays a part in stimulating fruiting and directing upward growth.