Navigating Mushroom Substrates

Before growing mushrooms, it is important to know which substrate is appropriate for the type of mushroom you are growing. Mushroom substrate is the equivalent of soil for plants, and is the necessary media used to grow mushrooms. In essence, mushroom substrate is the material needed to grow mushroom mycelia and acts as a source of nutrition, energy, water, and structural support necessary for the mycelia to produce fruits/mushrooms.

There are a variety of substrates used in mushroom cultivation, each providing different components necessary to grow mushrooms. Each mushroom species has its own preferences for substrates, so it is important to match the substrates to your mushroom species for optimal growth and yields.


The perfect substrate

Myterra Labs’ substrates are rigorously tested through scientific experiments to guarantee success across a broad range of cultivated mushroom species. But what truly defines a good mushroom substrate and how can you identify a good substrate before using it for mushroom cultivation?

  1. Mushroom substrates need to contain an adequate amount of moisture for mushrooms to grow and fruit. Mushroom fruits consist of ~90% water, all of which is obtained from the substrate. Without an adequate amount of water in the substrate, mushrooms will either produce a lower yield, abort, or dry out before they have reached a harvestable size. Mushroom substrates should be hydrated to field capacity, which means that puddles of water (excess water) should not be visible in the bottom of mushroom substrate bags. Excess moisture can promotoe bacterial growth during mushroom cultivation. You should be able to squeeze the substrate in your fist and obtain a few drops of moisture, and when you open your fist, the substrate should form a ball that is able to be broken when poked. Moisture can be lost from the substrate over time if the mushroom substrate bags do not have an airtight seal, and if the substrate bags have filter patches. Myterra Labs packages all substrates in external packaging that is air-tight to retain the moisture content of the substrate, providing you with substrate that is as fresh as the day it was produced.
  2. Mushroom substrates need to be free of competing organisms, A.K.A. contaminants. A contaminant is any organism (such as bacteria, yeast, viruses, and fungi) that inhibits or prevents mycelial growth and fruit-body formation of your cultivated mushrooms. Most contaminants are not visible to the human eye and some contaminants can be harmful to human health. Contaminated mushroom substrates can result in the partial/complete loss of your mushroom crop. Always check your mushroom substrate bags before using them to ensure that there is no discolouration or visible signs of growth in the bag prior to inoculating the bag with a mushroom culture. Assess the seal on your mushroom substrate bags to ensure that there are no leaks in the seal. Sterilizing mushroom substrate eliminates living organisms within the substrate; however, if the mushroom substrate bags are not sealed and packaged in a sterile manner after sterilizing, there is still a risk that your sterilized bag can contain contaminants. Myterra Labs seals and packages all its products in a HEPA-filtered clean room to ensure a sterile product that can be used in sterile laboratories.
  3. The structure of the mushroom substrate should allow for adequate air exchange. Mushroom mycelia requires gas exchange for optimal growth. The substrate should not be muddy and should fluff out when shaken or broken apart. Myterra Labs uses lignin-rich ingredients to add structure to the mushroom substrate, while still retaining maximum water-holding capacity.


Using mushroom substrates

Deciding how to use your mushroom substrate depends on the species that you want to cultivate and the cultivation space that you have available to you.

  • Growing in the bag: This method is ideal for most wood-loving species. After the addition of grain spawn into the fruiting substrate, the bag must be sealed, and left to colonize. This final bag of mushroom spawn and substrate is usually referred to as a fruiting block. Once colonized, the fruiting block should be placed in an environment with adequate fresh air, humidity and controlled temperature. The bag can then be cut open to stimulate fruiting.
  • Growing in a fruiting chamber: Mushroom fruiting chambers or monotubs are best suited for top-fruiting mushrooms. Mushrooms that have a high requirement for fresh air exchanges, such as oyster mushrooms, are less suited to this method of cultivation. It is extremely important to ensure that the mushroom fruiting chamber is cleaned and wiped out with 70 % isopropyl alcohol before use. Fruiting chambers offer mushroom cultivators an opportunity to grow mushrooms in environments that are not humidity controlled because most of the moisture released by the fruiting substrate and mushrooms is able to be retained in the fruiting chamber.
  • Garden bed: Certain mushroom species, such as wine caps, prefer cultivation in an outdoor garden bed. Simply dig out an area in a shady part of your yard and fill the hole with a layer of mushroom grain spawn, then mushroom substrate (eg. Woodlovers Blend), then wet cardboard. Spray the cardboard layer with a generous amount of water, then replace the topsoil over the hole and spray generously with water once more. The mushroom bed will need to stay moist and will require continual watering to prevent drying of the soil. Mushrooms will appear when the weather suits their preference, generally in the spring and fall.


What to do with spent mushroom substrate

When your mushroom substrates no longer produce enough mushrooms to warrant harvesting, or stop producing mushrooms altogether, they are “spent”. The most common choice for mushroom cultivators is to compost their spent substrates. It can be mixed into an existing compost pile to speed up the composting time. Large commercial mushroom cultivators will even sell spent mushroom substrates to composting companies to enhance their compost. Alternatively, spent substrates can be broken up and mixed in with your garden soil to promote soil health.