Boosting Your Mushroom Substrate with Supplements

Using mushroom substrate supplements can help you produce faster, bigger and healthier mushrooms.

In today’s article at the Garden Bench Top, we are going to be taking a deep dive into the different types of natural supplements that can take your mushroom growing to a whole new level.

So, if you have been struggling to grow a healthy flush of mushrooms OR you want to increase the chances of success as a mushroom hobby farmer, keep on reading.

mushroom substrate supplements

You can expect to learn:

  • the different types of mushroom substrate supplements,
  • how they benefit mushroom growth, and
  • things to watch out for when including supplements in your mushroom grow kit.

Why you Should be Adding Fertilizer to Your Mushroom Grow Kit

Adding mushroom substrate supplements to your growing kits is just like adding vitamins and minerals to your diet to improve your body’s health and function.

Supplements assist mushrooms to gain the necessary essential elements for a strong production of white mushroom mycelium, and ultimately a full flush of delicious mushrooms for you to enjoy.

Let’s take a closer look at how supplements assist mushrooms to grow.

Be in Control of your Mushroom Substrate

Supplements can help you to create a favorable environment that promotes healthy mushroom mycelium growth from your mushroom spawn.

For example, mushrooms prefer a slightly more acidic environment to thrive. So, by adding lime as a supplement to your mushroom substrate, you can naturally create higher acid conditions on almost any type of substrate. This affords you more control and an increased likelihood of a successful flush of mushrooms.

adding supplements to mushroom substrate

Natural Temperature Control

For those that live in colder climates, mixing supplements into your bulk substrate can help you to control the internal temperature of your mushroom grow kit.

A study by the Horticulture Department of Raparin University on using supplements in the growth of oyster mushrooms, found that by adding lime into the substrate helped to increase temperatures in the bags of oyster mushrooms. This helped to maintain a favorable environment, that allowed the mushrooms to grow quicker.

Gypsum and Mushroom Substrate – What is it?

Gypsum is a popular supplement that can often be found added to the mushroom grain spawn (the spores that you purchase to seed your growth medium).

You can also add gypsum directly to the mushroom bulk substrate to help with the inoculation phase of the mushroom growth cycle.

The chemical compounds of gypsum for mushrooms is dihydrate of calcium sulfate (chemical formula CaSO4 2H2O).

Benefits of Add Gypsum to your Mushroom Substrate

Gypsum and Mushroom Substrate

The reason why many hobby farmers include gypsum when growing mushrooms is that it provides a source of calcium for the mushroom spawn to use.

It was documented in a study by the National Center for Biotechnology Information that the addition of gypsum assisted to growing more mushrooms with a larger cap sizes and produced faster colonization.

How Much Gypsum to add to Mushroom Substrate

Depending on the type of substrate you are using in your kit, there may already be calcium present within the raw materials. So it is hard to provide an exact answer on how much gypsum to add to your mushroom substrate.

It is important to understand only a small amount of gypsum is required in order to provide enough calcium for your mushroom spawn to grow successfully. It is only a supplement.

A general rule of thumb is to use a ratio of 1:25 of gypsum to the total weight of your bulk substrate.

To provide an example, if you have a total weight of 5 kg of soil/compost/manure growing medium in your mushroom grow kit. Then you will add approximately 200 grams of gypsum to mix through your mix.

Do You Need Gypsum for Mushroom Substrate

Even though Gypsum is a popular supplement for most mushroom grower, it is not an essential ingredient that MUST be included in your grow kit.

Having said that, calcium is an essential ingredient for mushroom cultivation.

However, calcium can be included through other means, such as calcium carbonate (discussed further in this article).

What happens if you put in too much gypsum?

If you add too much gypsum to your substrate, you won’t see any immediate negative effects on your mushroom. What we mean, is that your mushroom spawn will still grow, and you will see baby mushrooms developing as you would expect.

Where you may notice some consequences of excess of gypsum is the yield size of your mushroom crop. The reason is mushrooms won’t grow on gypsum, only on the organic material such as straw or compost. So, adding too much gypsum will fill up space with uninhabitable material in your growing kit that would otherwise be colonized by the mushroom spore.

Calcium Carbonate and Mushroom Substrate – What is it?

calcium carbonate mushroom substrate
adding supplements increases mushroom growth

Calcium Carbonate, some farmers refer to as lime, is one of the important ingredients when it comes to successful mushroom cultivation. The reason both commercial growers and hobby fungi farmers use lime is to control the conditions of the growing medium (or substrate). We’ll look into how it impacts the growing medium more in the next section.

For all the scientifically inclined readers out there, Calcium Carbonate’s chemical compound symbol is CaCO3.

As you may have already gathered from the name, the chemical contains calcium, which is an essential element mushrooms require in order to grow. So, like gypsum above, some hobbyists use it as an additive for the calcium component.

Let’s now look at the advantages of using calcium carbonate in your DIY mushroom grow kits.

What are the benefits of using Calcium Carbonate in mushroom substrate?

Increase Calcium Content

We just mentioned calcium carbonate can be used to increase the calcium content in your substrate. If this is your primary purpose for adding calcium carbonate, we suggest only adding small amounts. This is because some substrates already have some calcium content.

Control pH Levels

Using calcium carbonate in your growing medium helps to control the pH levels. In fact, mushrooms tend to thrive in neutral (pH = 7) conditions. Therefore, if you have a more acidic environment, you can use calcium carbonate to neutralize the acidity and increase the alkalinity until you reach your desired pH level.

If you don’t know what your pH levels are for your mushroom substrate, you can purchase simple pH – test strips from your local chemist or online provider like Amazon.

Increase Mushroom Yield

An experiment detailed on Research Gate studied the impact of calcium carbonate on the growth and yield of oyster mushrooms. They found substrates that included amounts of calcium carbonate, yielded larger crops of mushrooms, than those without.

They concluded the calcium carbonate helped to stabilize the substrate and achieve a conducive growing environment for the mushroom spores to thrive.

How much Lime do I add to Mushroom Substrate

The answer to this question will depend on the purpose of adding lime to your bulk substrate.

If you are looking to raise pH (increase alkalinity) levels, you will need to purchase some pH test strips to ensure you are only adding enough lime (calcium carbonate) to attain a neutral environment of pH levels equal to 7.

On the other hand, if you are looking to use hydrated lime (calcium carbonate) for the purposes of increasing the calcium content of your mushroom substrate (like coffee grounds), then we would recommend only using a small amount.

Similar to adding gypsum, we recommend apply the general rule of using a ratio of 1:25 of lime to the total weight of your substrate.

To provide an example, if you have a total weight of 5 kg of soil/compost/manure growing medium in your mushroom grow kit. Then you will add approximately 200 grams of lime to your substrate mix.

How much water do I add to a Mushroom Substrate?

adding water to substrate
be careful not to add too much water

In general, water should not be added directly to your mushroom growing kit. Mushrooms like a moist environment, but not a water laden soggy growing medium.

You want a particular level of moisture in your mushroom substrate, however this should be added before you begin constructing your DIY growing kit.

We usually recommend soaking your growing medium in a hot water bath overnight, such as wood chips or straw. In the morning, simply allow the excess water to drain away, and the moisture content in the substrate will be sufficient for the mushroom spores to grow.

What Next?

Now that you know the different types of mushroom substrate supplements that can be added to your DIY home grow kit, the next step is work out what type of substrate you are going to use.

You can also find some of our favorite mushroom substrate recipes on our substrate deep dive.