How To Grow Hydroponic Mushrooms

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By Chris Lipsey

Mushrooms might not be the first crop people think about growing at home. But you can, and you can also produce them hydroponically. However, fungi are grown completely differently from other plants, so there are a number of differences in the grow setup.

You’re probably used to the idea that mushrooms like to grow in the dark, damp places, but you might not know that they require a lot of care and attention to detail.

And by the way, mushrooms have no roots but rather a mycelium network.

Mycelium is a network of fungi threads. They are present in soil and help break down organic matter. In fact,  92% of all plant families interact with one or other fungi. The mushroom part we consume is actually the fruiting part of this network.

Before we go further what are the benefits of growing mushrooms hydroponically? After all, they don’t need light, space, or fertilizer. So why?

Related: Best Hydroponic Plants – Top Herbs, Vegetables, and Fruits To Grow Hydroponically

Why Grow Mushrooms Hydroponically?

Growing mushrooms hydroponically means there’s no need for grow lights. While these fungi require some light, they don’t need the same levels as plants.

As we mentioned, mushrooms like cool, dark, and humid growing conditions. They also feed on their growing media, which needs to be kept moist, and the mycelium will need to be able to access sugar, fat, lignin, starch, nitrogen, as well as protein in order to grow well. All you have to do is make these nutrients available in the growing media.

While for most of a mushroom’s life it requires little to no light for development, it will require a little when fruiting. Don’t use grow lights, as this is too intense for the fungi. Rather use a low power fluorescent lamp, or indirect sunlight.

With these limited requirements, mushrooms are a simple crop to grow if the conditions are correct.

If you are interested in growing hydroponic mushrooms, you will either need to buy an inoculated brick, or create one yourself.

The latter is fairly complex, but let’s go through the steps so you know. We’d recommend purchasing a kit that’s ready for use, but that being said…

How To Inoculate Your Own Substrate

Creating your own mushroom brick is an art. It requires keeping surfaces, tools and the substrate perfectly clean. Any contaminants will ruin the entire process.

When starting to prepare the substrate you need to ensure that it is cleared of any rogue fungi. This means your substrate, which can be:

  • Logs
  • Stumps
  • Woodchips
  • Straw
  • Sawdust
  • Coffee grounds
  • Grain hulls
  • And other carbon-rich materials

Must be boiled, or treated with a bacteria clearing agent.

Mushrooms don’t produce seeds but rather propagate via spores (or spawn). These spores are microscopic and sometimes can be seen in dust clouds when dispersed.

The inoculation process is where you bring the spawn into contact with the treated substrate. A generalization when inoculating substrates is that the outdoor varieties require less sterilization compared to mushrooms grown indoors, which is how we’ll be growing our mushrooms hydroponically.

When inoculating your substrate, there are three factors to consider:

  • Where you inoculate
  • Inoculation rates
  • Spawn distribution

Where You Inoculate

The location of the inoculation refers to where you’re growing the mushrooms and their access to nutrients in their substrate.

With logs, stumps, woodchips, and straw, you’ll be growing outdoors, and the mushrooms will be feeding on low-nitrogen, carbon-rich materials. Make sure to keep surfaces and hands clean but sterilization is not necessary.

But when it is indoors, sterilization is absolutely vital. You will need to work in lab conditions. This is because the substrate will be more nitrogen-rich and is susceptible to natural microorganisms.

For small scale, you will be fine with just mimicking lab conditions. But for an industrial scale grow, you will need a high-efficiency particulate air filter.

Mushroom Inoculation Rates

Inoculation rates refer to the speed with which the mycelium takes to the substrate. You want your edible mycelium to be established before any wild outside contaminates, like yeasts. If your rates are lower, you can give your substrate a boost with more spores.

While this will boost the chances of your mushrooms winning the mycelium development race, it is also a costly exercise. However, high inoculation rates are advised for new growers just to improve their chances of a good harvest and reduce risks. Over time you will get used to the conditions and know the exact amount to add.

Normally these inoculations would be administered via injection or lab-grown spawn. So yes, growing mushrooms from mycelium is more complicated than growing veggies from seed.

Spawn Distribution and Mushroom Inoculation

Spawn distribution is how you scatter the spores. There are two methods, top, and through-spawning.

Top spawning is done by scattering the spores on the top layer of substrate and allowing them to grow down. This method is great for mason jars or low-stake cultivation.

Through-spawning is when you shake the substrate with spawn to ensure it is evenly distributed in.

If you want the most out of your substrate we’d suggest taking the through-spawning technique and even layering it.

This will require more spawn, but again, over time you’ll learn the right ratios and use less.

Now that you understand why you should grow mushrooms hydroponically, and how to inoculate your own system, let’s focus on the lifecycle of a mushroom.

Mushroom Life Cycle

There are two stages to a mushroom’s life. The first is:

The Vegetative Stage

By now you will know that when spores meet the substrate they will start to form networks, otherwise known as threads of cells called hyphae. If you’ve treated your substrate well, the hyphae should be able to feed on it and expand.

These networks will form a mycelium. You want to cultivate this network and allow it to form strong connections. This is the root of the “plant” and it needs to be healthy.

This network will join together creating pinheads, which are tiny baby mushrooms.

Then comes the second stage.

The Fruiting Stage

Under the right conditions, these pinheads will develop into fully-formed mushrooms, or go into the fruit stage of their lives.

This fruit will distribute spores that will again float through the air and land on any fertile substrates, and repeat the life cycle.

The mushroom is the above-ground sexual organ of the mycelium network, which wants to expand. In Oregon, the Humongous Fungus (a honey mushroom) set a record as one of the largest single living organisms, at 3.5 square miles large (this was estimated). This fungus spreads through the underground network infecting and killing trees.

But no need to worry, mushrooms can’t take over an entire system. This is because mushrooms can’t create their own food like plants. So, when the network has consumed all the organic matter it collapses and dies.

Ok, let’s get down to what equipment you’ll need to grow mushrooms that won’t kill whole trees.

Hydroponic Equipment Needed To Grow Mushrooms

When preparing your hydroponic system for mushrooms you want to mimic the optimum growing conditions in the wild.

Your substrate and network will be happiest if the temperature hovers around 75°F to 80°F, and up to 85°F when fruiting.

Humidity will need to be high, around 70% to 90%. This means creating a closed-off area that can retain moisture, thus the use of plastic for mushroom kits.

The equipment you will need is:

  • Glass container
  • Water reservoir
  • Lightweight Expanded Clay Aggregate (LECA)
  • Water heater
  • Humidity gauge
  • Light
  • And air pump with an airstone

Your hydroponic system will basically be a deep water culture (DWC), but slightly different.

At the bottom of the reservoir place, your airstone and water heater. Cover the water with a layer of LECA. The LECA should allow the inoculated cakes to float on top.

The air pump will provide air to the substrate, and the heater will keep the temperature at an optimum level.

When the mycelium starts to show pinheads, turn on your light to coax the fruit out.

The last step with the light can vary depending on the mycelium you’re growing. There is currently research being conducted about what type of light is the best for fruiting mushrooms. You should probably play around with your lighting to see what works best.

If you’re keen to start growing your own mushrooms, we’d recommend purchasing a kit from Amazon.

Now You Know You Can Grow Mushrooms Hydroponically

Growing mushrooms is far beyond the usual horticulturist’s expertise, but it is fun and doable with the right setup. It’s just a completely different skillset to master.

Also, mushrooms require a completely different way of thinking when it comes to propagation and growth.

And if you were wondering, yes, their substrate can be reused in the garden.