How to Grow Mushrooms in a Jar

There are different methods to grow mushrooms, but one of the most practical and economical is cultivation in glass jars.

In this article I will explain how to do it step by step and I will answer some frequently asked questions on this topic.

Why Grow Mushrooms in a Jar?

Growing mushrooms in a jar has several advantages:

• It is an easy and fast method that does not require much space or materials.
• It is a way of taking advantage of organic waste such as coffee grounds or straws, which serve as a substrate for mushrooms.
• It is a way to obtain fresh and organic mushrooms throughout the year, without depending on the season or the weather.
• It is a fun and educational activity that we can do with children or adults.

What Do We Need to Grow Mushrooms in a Jar?

To grow mushrooms in a jar we need the following materials:

• A glass jar with a metal lid, preferably dark or covered with black plastic to prevent light from entering.
• A suitable substrate for the mushrooms that we want to grow, such as coffee grounds, straw, sawdust, or paper.
• A mycelium or mushroom seed, which we can buy in specialized stores or online.
• A spray with water to maintain the humidity of the substrate.
• A knife or scissors to poke holes in the jar lid.

How to Prepare the Substrate for Mushrooms?

The substrate is the medium where the mushrooms grow and must have certain characteristics to favor their development:

• It should be damp but not soggy, as excess water can cause mold or bacteria to grow.
• It must be sterilized or pasteurized to eliminate possible contaminants that compete with mushrooms. We can do it by boiling the substrate for about 20 minutes or putting it in the microwave for about 10 minutes.
• It must be well mixed with the mycelium or mushroom seed, distributing it evenly throughout the substrate.

How to Fill the Jar With the Substrate and the Mycelium?

Once we have the substrate prepared, we can proceed to fill the jar with it by following these steps:

• Wash the jar and lid well with soap and water and dry well.
• Poke about 10 small holes in the lid with a knife or scissors. These holes will allow air to enter the jar and the carbon dioxide produced by the mushrooms to breathe out.
• Fill the jar with the substrate mixed with the mycelium, leaving about 2 cm free at the top. Do not press the substrate too much, since it must be spongy to facilitate the growth of the mushrooms.
• Close the jar with the perforated lid and cover it with black plastic if it is not dark.

 

How to Care for the Jar With Mushrooms?

Once we have the bottle ready, we must place it in a suitable place and follow these care instructions:

• Choose a place where the temperature is between 15 and 25 ºC, depending on the species of mushroom that we have chosen. Avoid very cold or very hot places, since they can affect the growth of the mushrooms. Some of the optimal temperatures for the most common mushrooms are:
  • Oyster mushroom between 16 and 22 ºC
  • Shiitake between 14 and 20 ºC
  • Portobello between 18 and 22 ºC
  • Chanterelle between 15 and 18 ºC
• Keep the jar away from direct sunlight, as this can dry out the substrate or inhibit the development of mushrooms. Ideally, the jar receives dim or indirect light.
• Moisten the substrate with the sprayer at least once a day, without flooding it. The substrate must always be moist but not wet, as excess water can cause mold or bacteria to appear.
• Observe the bottle periodically to check for signs of contamination or mushroom growth. If we see that the substrate changes color or smells bad, it may have been contaminated and we should discard it. If we see that some white or brown bumps appear in the substrate or in the holes in the lid, it is possible that they are the mushrooms starting to come out.

How to harvest mushrooms?

The time it takes for the mushrooms to come out depends on the species, the temperature, and the humidity of the environment. It can vary from a few days to a few weeks.

The normal thing is that the mushrooms come out through the holes in the lid, but they can also do so through the edge of the jar or through the interior of it.

To harvest the mushrooms, we must wait for them to be of a suitable size and for the caps to open. We should not let them grow too long, as they can lose flavor and texture. Nor should we pluck them with force, since we can damage the mycelium and hinder the production of more mushrooms.

The correct way to harvest the mushrooms is by gently turning them until they detach from the substrate. Then, we must clean them with a damp cloth or a soft brush to remove the remains of the substrate. It is not recommended to wash them with water, since they can absorb it and lose quality.