Sterile substrates (or 'subs' for short) are any mushroom food, such as sawdust, wood chips, or manure that has been treated in order to remove contaminants prior to inoculation with the desired mushroom spawn. Recall from our blog post on common contaminants the importance of sterile technique in eliminating rival bacteria, molds, and even animal pests such as fungi gnats and fruit flies. We offer a step-by-step guide to pasteurizing substrates in our bucket tek post, and an overview on how to sterilize your substrates using an All-American pressure sterilizer.
In this article, we get into the sterile substrates and substrate supplements we produce and share our mushroom-substrate compatibility guide. Sterile substrates are the second most important ingredient in mushroom cultivation, after the mushrooms themselves, so pay attention! This information is intended to help you make informed decisions about legal edible and medicinal mushroom cultivation. North Spore's products shall only be used for lawful purposes. North Spore does not condone hallucinogenic mushroom growing in jurisdictions where it is illegal.
Mushroom substrates and supplements
Recall from our introduction to fungal biology article that mushrooms reproduce through spores which can be isolated on sterile media, grown on grain to produce grain spawn, and mixed into supplemented, sterilized substrate to colonize and fruit mushrooms. If you choose to grow mushrooms directly from spores, you'll need to know the difference between spores and spawn and some basic mycology lab skills. Sterile substrates include grain bags, all-in-one bags, manure-based substrate, and hard wood-based substrates, including Mastr Mix which can be used to make fruiting blocks.
Grain spawn often contains a mix of several grains.
Once the mushroom culture is introduced to a grain bag and begins colonizing it, it becomes grain spawn. Grain is relatively inexpensive to procure and full of nutritional energy; perfect food for a young mycelium. Grain spawn is often housed in a transparent container such as a clear filter patch bag or mason jar for easier monitoring. Grains including brown rice, rye berries, wheat berries, millet, barley, oats and even corn are used to make grain spawn. In selecting grain for this purpose it is important to note that grain size factors into colonization speed, as smaller grains have more inoculation points and mix more evenly into a bulk substrate.
Our Wood Lovr substrate contains a mixture of lignin and cellulose.
Many of our favorite edible and medicinal mushrooms such as shiitake, oyster, and reishi feed on decaying organic matter, specifically the tough lignin, cellulose, and hemicellulose that make up plant cell walls. As decomposers, they play an important role in ecosystem functioning by breaking down organic matter and recycling it back into the soil. Manure, compost, sawdust, straw, wood chips, hardwood dowels, logs, leaf litter, and cardboard are full of this material and make excellent bulk substrates, as do agricultural byproducts such as coffee grounds, cotton shells, sugar cane fiber, sugar beets, corn stalks, coconut husks, and soybean hulls. Substrates that are compatible with these supplements include Wood Lovr (hardwood-based sterile substrate) and Mastr Mix (formulated for fruiting blocks of hardwood-loving species).
Hardwood pellets, a common bulk substrate & supplement.
Cultivators supplement their bulk substrates with nutrients to enhance mushroom growth and development. Since mushrooms are 80 to 90 percent water, this is a key nutrient and is added early in the substrate-building process. Moisture content of bulk substrates should be between 50 and 70% and materials such as coco coir, vermiculite, hardwood pellets, and soybean hulls are often added to substrates to increase water retention. Nitrogen is a basic building block of proteins and is therefore critical to mushroom growth. Common nitrogen supplements include soybean meal, cottonseed meal, and corn meal in addition to soybean hulls, wheat bran and oat bran which are also rich in carbohydrates and B vitamins. Additional substrate supplements include gypsum for calcium and sulfur, limestone to adjust pH (many mushrooms grow best in a slightly acidic environment), and mineral supplements like potassium, magnesium, and iron sulfates for growth.
Soy hull pellets are a popular substrate supplement and a good source of nitrogen.
Sterile substrates, grow methods, and compatible species
Our beginner-friendly all-in-one mushroom grow bag contains a proprietary blend of sterilized, nutrient-rich, organic manure-based compost, organic grain, coco coir, and several quality substrate supplements formulated to simplify mushroom growing while maximizing the speed and size of your grow. Just inject, grow, harvest-the entire process takes place directly in the bag!
Organic Sterilized Grain Bag with Injection Port
One of our best-selling products is a proprietary blend featuring hydrated, nutrient-rich, organic millet and wheat berries. Each grain bag also includes a self-healing injection port for use with a spore or culture syringe plus a 0.2 micron filter patch to block airborne contaminants while providing even gas exchange. We recommended 1 lb of colonized grain spawn for every 5 lbs of manure or hardwood sterile substrate. We also recommend using 2.5-5ccs per 3 lb injection port bag. Millet is less prone to contamination than rye and wheat, and its small size provides more inoculation points for the same volume of grain, encouraging rapid mycelial expansion. Grain spawn can be used to inoculate other sterile substrates.
‘Wood Lovr’ Organic Hardwood Sterile Mushroom Bulk Substrate
This is a hydrated, wood chip-based substrate formulated for hardwood-loving species. Our blend combines a range of particle sizes with nitrogen supplementation to speed up growth and maximize yield. Wood Lovr can be used in monotubs, trays, buckets, and containers in a humidity-controlled grow room such as our BoomRoom II. We recommend mixing 1 colonized grain spawn bag with 2-3 Wood Lovr bags. Wood Lovr can be mixed with hardwood sawdust to grow Lion's Mane and Nameko indoors, and mixed with wood chips to grow Pioppino indoors. When mixed with sawdust and cardboard, Wood Lovr can also be used to grow Chestnut mushrooms indoors. It can also serve as a nutritional supplement to other bulk substrates in outdoor bed cultivation of hardwood loving species such as Lion's Mane, Oysters, and Shiitake. Wine Cap is especially fond of outdoor beds composed of Wood Lovr and straw.
'Mastr Mix' Master's Mix Hardwood-Based Bulk Substrate
Our premium, hydrated and sterilized blend of hardwood sawdust, non-GMO soyhulls, and substrate amendments is formulated for a faster mycelial run and higher yields. This is an ideal bulk hardwood substrate for use with any compatible grain spawn strains and can be used to fruit straight from the bag in a controlled environment such as a grow tent or monotub.
‘Boomr Bag’ Manure Sterile Mushroom Bulk Substrate
The Boomr Bag, named for any mushroom that grows rapidly, is a sterilized and hydrated, proprietary blend of composted horse manure, coco coir, and several quality substrate supplements used in the cultivation of nutrient-rich or dung-loving mushroom species. Boomr Bag can be used in monotubs (check out our complete monotub tek guide), filter bags, and outdoor beds, or inoculated with grain spawn and top fruited in a humidity-controlled grow room such as our BoomRoom II. We recommend mixing 1 colonized grain spawn bag with 2-3 Boomr Bags.
Oysters and Black King can be grown in monotubs on a mixture of Boomr Bag, sterilized manure, hardwood sawdust and a number of agricultral byproducts. Almond agaricus and Blewit may be cultivated outdoors in beds using a blended mixture of Boomer Bag, leaf litter, sawdust, kitchen scraps, grass clippings, cereal straws, and agricultural byproducts like bean hulls or corn stalks. We have had some success cultivating Almond agaricus indoors in monotubs using a combination of Boomr Bag, sterilized manure, and nitrogen-supplemented compost.
Substrate Supplements
We carry a variety of non-sterile bulk substrate supplements to ensure healthy mushroom growth and development, including hardwood pellets, coco coir, millet, soy hull, and fluted hardwood dowels.
Hardwood pellets can be used in sawdust spawn and block production, or as a substrate supplement to improve water holding capacity. It is also an excellent source of lignin, a component of plant cell walls favored by oysters and lion's mane.
We carry a variety of non-sterile bulk substrate supplements to ensure healthy mushroom growth and development, including hardwood pellets, coco coir, millet, soy hull pellets, vermiculite, and fluted hardwood dowels. Hardwood pellets can be used in sawdust spawn and block production, or as a substrate supplement to improve water holding capacity. It is also an excellent source of lignin, a component of plant cell walls favored by Oysters and Lion's Mane. Coco coir, a non-sterile substrate that provides moisture retention and is highly resistant to contaminants, is often combined with manure-based bulk substrates and used as a casing layer in colonized monotubs. It can also be used in garden beds as an alternative to peat moss. Nutritious, small in size and relatively inexpensive, millet can be used for making mushroom spawn or as a substrate supplement. Its small size provides more inoculation points for colonization and readily absorbs water. Soy hull pellets have excellent water retention and are a good source of protein and nitrogen, which has been shown to increase crop productivity. Vermiculite can be added for additional moisture retention and promotes airflow in the substrate. It is typically blended with hardwood sawdust to produce fruiting blocks. Hardwood dowels are ideal for mushroom plug spawn production and used in log inoculation. They are kiln dried but not treated in any other way.
Coco coir is a non-sterile substrate that provides moisture retention and is highly resistant to contaminants, is often combined with manure-based bulk substrates and used as a casing layer in colonized monotubs. It can also be used in garden beds as an alternative to peat moss.
Nutritious, small in size and relatively inexpensive, millet is used for making grain spawn. It's small size provides more inoculation points for colonization and readily absorbs water.
Soy hull has excellent water retention and is a good source of protein and nitrogen, which has been shown to increase crop productivity. It is typically blended with hardwood sawdust to produce fruiting blocks.
Hardwood dowels are ideal for mushroom plug spawn production and used in log inoculation. They are kiln dried but not treated in any other way.
Final thoughts
Once you decide which mushroom variety is right for you, you'll need to determine the correct substrate to use, and our helpful substrate compatability guide provides growing locations, grow methods, and compatible indoor and outdoor substrates for 15 of our most popular strains, from Almond agaricus to Wine Cap. Our sterilized grain bags, Wood Lovr, Boomr Bags, and ShroomTek, and Mastr Mix are an excellent way to get started in growing out your chosen mushroom variety, and you can boost your grow with our supply of nutrient-rich substrate supplements. If you have any questions, comments, concerns, or even a new way to grow a particular mushroom, please reach out! We are here to support you on your mushroom growing journey.