- 🌱 Mushrooms don't need light to spread, but light is important when they fruit.
- 💡 A 12-hour light/dark cycle copies nature and helps mushrooms grow well.
- 🌾 Blue-spectrum LEDs (450-470 nm) make oyster mushroom caps grow better.
- 🌞 Direct sunlight or heat can dry growing material and stop mushroom production.
- 🏠 You can grow mushrooms at home well with simple lights.
When people picture mushroom growth, they often imagine dark forests or damp caves. But in home mushroom cultivation, light is one of the most important environmental triggers. Unlike plants, mushrooms don’t photosynthesize, yet they still rely on light signals to know when to form fruiting bodies. The right type, timing, and intensity of light can mean the difference between weak, uneven growth and a flush of healthy, well-shaped mushrooms with higher yields. And when paired with mushroom spawn bags, which provide a clean and nutrient-rich start, proper lighting helps cultivators get the most out of every flush.
The Mushroom Life Cycle: When Light Matters
To understand why and when light is important for mushroom growth, it's good to know about the two main stages of a mushroom’s life: vegetative growth and reproductive growth.
🧫 1. Vegetative Growth (Mycelium Spreading)
In this first stage, mushroom spores sprout and grow into mycelium. This is the root-like network that spreads through organic material like wood, straw, or grain. Mycelium doesn't need light to grow well. In fact, it grows best in the dark with steady temperatures. This lets it spread well through the substrate. Mycelium growth takes in food and gets ready for mushrooms to grow.
During this stage, the environment needs:
- Darkness or low light
- Steady humidity
- Steady temperature for the specific mushroom type
- Little disturbance
🍄 2. Reproductive Growth (Fruiting)
Once the mycelium fully spreads through its substrate, and it gets the right environment, it starts to make primordia. This usually means fresh air, less CO₂, and more humidity. These are also called pinheads.
This is where light becomes very important.
Paul Stamets explains in his important book Growing Gourmet and Medicinal Mushrooms that light is the main signal to start primordia. Without light, the mycelium may fruit later or not grow mushrooms at all. This is because it doesn't get an outside sign that it's safe to make more mushrooms (Stamets, 2000).
Why Light Affects How Mushrooms Look and Grow
You don’t need ultraviolet sunlamps or heat sources to make mushrooms grow. But getting the right kind of light makes sure your mushrooms grow properly. Here's how light affects growth when mushrooms are fruiting:
📍 How Light Directs Growth
Mushrooms do not use sunlight for food, but they grow toward light. This means they are phototropic. When light is added during fruiting, mushrooms point themselves toward it. Without light, mushrooms may grow sideways, downward, or have twisted stems. This happens because they are trying to find light.
🎨 Color
Light affects the natural color of many mushroom types. Not enough light makes them pale or have odd colors. But the right light helps them get rich, deep colors. These colors show they are healthy and ready to pick.
Examples include:
- Blue oyster mushrooms turning a dull gray in low light
- Enoki mushrooms staying white if they don't get full-spectrum light
🏋️ Cap and Stem Growth
Without light, stems often become long and weak as they reach for light in the dark. It is like a plant that grows too tall and thin with not enough light. Steady, soft light lets caps form fully. It also helps stems grow thick and strong.
So, Do Mushrooms Need Light to Grow?
Let's clear up a common idea: mushrooms don't need light to "feed" themselves like plants. But light is clearly a signal for them to grow.
✅ Light Is Not Required for:
- Mycelium spreading
- Getting food or cell energy
- Spores to first sprout
❗ Light Is Required for:
- Starting fruiting after spreading is done
- Right direction and cap growth
- Healthy color and tissue growth
If you skip light during the fruiting stage, even the best substrate can give you a small harvest of thin, poorly formed mushrooms. They will not be what you hoped for.
How Much Light Do Mushrooms Need?
Mushrooms don't need a lot of light. So you can grow them inside, even in small apartments or kitchens. But it must be the right kind and for the right amount of time.
🕒 Recommended Light Cycle
A 12 hours on / 12 hours off light cycle works well for most mushroom types when they are fruiting. This cycle copies natural day and night. It shows the mushrooms it is okay to fruit.
💡 Type of Light to Use
You don't have to spend a lot on special grow lights. What works:
- Indirect sunlight (but not direct sun!)
- Cool-running LEDs
- Fluorescent lamps (full-spectrum)
Don't use high-intensity discharge bulbs or infrared heat lamps. These can harm the steady environment and make the temperature too hot for most mushrooms.
🔵 Blue Light (450–470 nm)
A 2015 study by Nishizawa, Uesaka, and Koyama showed that blue light in the 450–470 nm range greatly helps the size and shape of oyster mushrooms (Pleurotus ostreatus). This makes for bigger caps and healthier mushrooms.
🌞 Avoid Direct Sunlight
Natural sunlight may seem easy, but it’s often too strong. South-facing windows can greatly raise the heat around your grow kit. This causes the substrate to dry out and stops mushroom growth.
Best Lighting Setup for Indoor Mushroom Growing
You don’t need a greenhouse or a special grow room to grow mushrooms well at home. Making a good setup often needs only a few simple parts.
🧰 What You’ll Need
- LED Strip Lights: Cheap, use little power, and stay cool
- Timer: Set your lights to turn on and off automatically. This keeps things steady.
- Shelving or Stand: To lift kits up and put lights at the right spot
- Reflective Surround: White surfaces or aluminum foil can help spread light
💡 Placement Tips
- Mount lights 6–12 inches above the fruiting surface of the grow kit.
- Choose full-spectrum or blue-dominant LEDs, especially for oyster mushrooms.
- Install a light diffuser if the light is too strong and causes drying or overheating.
Steady, soft light right above your grow kits helps all pins grow at once and makes caps grow better.
Which Mushrooms Like More (or Less) Light?
Lighting needs are not the same for all. Some types grow well with bright light, while others like soft, spread-out light. Here is a list to help you pick the right mushroom type for your grow setup.
| Mushroom Species | Light Preference | Notes |
|---|---|---|
| Oyster | Moderate to High | Does well with blue light, grows fast |
| Shiitake | Moderate | Needs light for pins and shape |
| Lion’s Mane | Low to Moderate | Soft light is best; bright light makes it grow slower |
| Enoki | Very Low to Moderate | Grows white in low light, golden in bright |
When choosing a type to grow mushrooms at home, always think about your home's natural light or how much man-made light you can give it.
What Happens with Too Much or Too Little Light?
A balanced environment is key to growing mushrooms. Even good things like light, if used too much or too little, can cause problems.
🚫 Too Little Light:
- Long, weak stems
- Small caps, or no caps at all
- Mixed-up growth, not pointing the right way
🚫 Too Much Light or Heat:
- Dry substrate
- Cracked caps
- Growing old too fast or changing color
How to stop too much light or heat:
- Don't use strong sunlight from south-facing windows
- Don’t use incandescent bulbs
- Check humidity and temperature often. This will stop accidental drying.
Don’t Forget: Light is Just Part of the Equation
While lighting helps fruiting, many other important things must be right for mushrooms to grow well:
| Species | Ideal Temp | Humidity | Light Need |
|---|---|---|---|
| Oyster | 18–24°C (65–75°F) | 85–95% RH | Moderate to High |
| Lion’s Mane | 15–22°C (59–72°F) | 80–90% RH | Indirect Light |
| Shiitake | 15–21°C (60–70°F) | 75–85% RH | Moderate Light |
In addition:
- Fresh Air Exchange: Important for getting rid of CO₂ when fruiting.
- Stable Humidity: Use humidity domes or misting to keep it at 80–95%.
Zombie Mushrooms’ grow kits come with built-in humidity domes or airflow slits. This makes them good even for people growing for the first time.
Lighting Tips for Grow Kits and Small Spaces
Now that you know the basics, here’s how to use the best mushroom lighting in small, real-world spots.
🛠️ Practical Tips:
- Window Placement: North-facing windows give soft light.
- Artificial Light: Clip-on LED lamps or countertop grow lights work well.
- Automate with Timers: No need to guess. Set your lights on a timer.
- Keep Kits Elevated: Lowers the chance of cold air or too much water gathering.
Zombie Mushrooms’ kits are small and can fit in many places. They let you grow mushrooms at home even in places like a laundry room shelf or kitchen cabinet.
Busting the "Mushrooms Grow in the Dark" Myth
The phrase “mushrooms grow in the dark” doesn't tell the full story of what they need. Here's the truth:
- ✅ Mycelium: Yes, it grows well in the dark.
- ❌ Fruiting Mushrooms: No, they need light signs.
Mushrooms grew over time to fruit when they reach open air. That’s why light signals are very important. Brands like Zombie Mushrooms make each kit to help natural growth with the right light at each stage.
Choosing the Right Grow Kit Based on Your Lighting Conditions
When you’re just starting to grow mushrooms at home, picking the right type for your home can make the difference between a good time and bad results. Use this guide to find a match for your setup:
| Environment | Suggested Species | Why It Works |
|---|---|---|
| Bright kitchen w/ daylight | Shiitake, Cordyceps | These mushrooms like a fair amount of light |
| Low light shelf or hallway | Lion’s Mane | Grows well with very little light |
| Desktop LED on a timer | Oyster mushrooms | Easy to grow and grows fast under LEDs |
FAQ: Do Mushrooms Need Light to Grow?
Q1: Do mushrooms need light to grow?
No—mushrooms don’t need light to feed or colonize. Light becomes important only during the fruiting or reproductive stage, as a signal for correct form and orientation.
Q2: When does light become critical in the mushroom life cycle?
Light is most important after full substrate colonization, when primordia (pinheads) form. It helps guide cap development, stem thickness, and growth direction.
Q3: What kind of light and how much do mushrooms need?
Most mushrooms do well with a 12-hour light / 12-hour dark cycle using indirect or cool white LEDs. Blue spectrum light (450–470 nm) especially helps with cap size and healthy growth in species like oyster mushrooms.
Q4: Can too much light harm mushroom growth?
Yes. Direct sunlight or high intensity bulbs can overheat the substrate, dry it out, or damage developing primordia. Mushrooms prefer soft, diffused light rather than harsh, direct exposure.
Q5: Can mushrooms grow in total darkness?
Mycelium (the vegetative network) can grow in darkness, but for fruiting mushrooms, absence of light often leads to malformed or weak fruits. Light is a key trigger for proper development.
Light: A Simple Spark for a Great Grow
Light won’t feed your mushrooms—but it helps them grow. If you've ever tried and failed to grow mushrooms at home, it's likely light was the problem. If you start with a kit or grow a lot with bulk substrate, knowing and managing how much light mushrooms need will help you get good harvests you can count on.
With easy setup and kits that work well with light from Zombie Mushrooms, now is a great time to light up your growing space.
Let there be (just the right amount of) light.
Citations
Stamets, P. (2000). Growing Gourmet and Medicinal Mushrooms (3rd ed.). Ten Speed Press.
Carris, L. M., Littlefield, L. J., & Stiles, C. M. (2012). Introduction to Fungi. Cambridge University Press.
Nishizawa, Y., Uesaka, K., & Koyama, Y. (2015). The effect of LED light of different wavelengths and intensities on the growth and morphogenesis of Pleurotus ostreatus. Journal of Mushroom Science and Biotechnology, 23(2), 45-49.
