Organic Mushroom Farming and Mycoremediation: Simple to Advanced and Experimental Techniques for Indoor and Outdoor Cultivation

Praise for Organic Mushroom Farming and Mycoremediation

This is a reference book for the next generation of DIY mycologists. It is a great practical guide to mushroom cultivation, starting with basic concepts and building from there to mycoremediation and experimental strain development. Tradd Cotter is a man with a mission, who has done and thought about all this a lot; he has learned to explain it with great clarity and in a simple and well-organized manner.

—SANDOR ELLIX KATZ, fermentation revivalist and author of The Art of Fermentation and Wild Fermentation

Tradd Cotter has written a clear, comprehensive guide that is a gift to amateur as well as professional mushroom growers. The pages are enlivened by Cotter’s enthusiasm for the many possibilities that fungi offer, and his obvious familiarity with growing these marvelous creatures—not just theoretical knowledge—makes the book particularly valuable. This book opens the doors wide to a diverse and fascinating fungal world.

—TOBY HEMENWAY, author of Gaia’s Garden: A Guide to Home-Scale Permaculture

Finally, an accessible resource covering a wide variety of mushroom-cultivation approaches. Tradd Cotter’s book fills an enormous need—I’ve been wishing for a resource like this for a long time. This is the kind of book I’ll keep nearby and will turn to often over the years. Any farmer or gardener who wishes to garner food or medicine value from wood needs to understand and cultivate mushrooms. And this is the best all-around manual I’ve seen.

—BEN FALK, author of The Resilient Farm and Homestead

Wow! Tradd Cotter is a genius of organic mushroom production. His step-by-step instructions and beautiful photography make this a must-have book.

—ROBERT ROGERS, author of The Fungal Pharmacy: The Complete Guide to Medicinal Mushrooms and Lichens of North America

"Mushroom cultivation should be playing a much bigger role in our gardens and farms. Tradd Cotter’s Organic Mushroom Farming and Mycoremediation provides low-cost, easily accessible techniques for growing mushrooms indoors and outdoors, from home to commercial scale."

—ERIC TOENSMEIER, author of Paradise Lot and Perennial Vegetables

"Tradd Cotter has done a wonderful job sharing his practical experience in a well-organized way with illustrations that clearly underline the topics. Organic Mushroom Farming and Mycoremediation is an invaluable resource for teaching students about mushroom cultivation."

—PETER OEI, author of Mushroom Cultivation and director of horticulture innovation at InnovatieNetwerk, Dutch Ministry of Economic Affairs, and founder of MeattheMushroom.nl and spore.nl

"Organic Mushroom Farming and Mycoremediation is a guide and inspiration for new and experienced mushroom cultivators alike. Tradd Cotter has done a great job of combining the complexity of mushroom cultivation with the intuitive simplicity of ‘small steps.’ Highly recommended for fungophiles as a great read and reference!"

—JIM GIBSON, past president, Colorado Mycological Society

Organic Mushroom Farming and Mycoremediation

SIMPLE TO ADVANCED AND EXPERIMENTAL TECHNIQUES FOR INDOOR AND OUTDOOR CULTIVATION

AuthorL TRADD COTTER AuthorR

Chelsea Green Publishing

White River Junction, Vermont

Copyright © 2014 by Tradd Cotter.

All rights reserved.

Unless otherwise noted, all photographs and illustrations copyright

© 2014 by Tradd and Olga Cotter.

No part of this book may be transmitted or reproduced in any form by any means without permission in writing from the publisher.

Developmental Editor: Brianne Goodspeed

Project Manager: Patricia Stone

Copy Editor: Nancy Ringer

Proofreader: Laura Jorstad

Indexer: Shana Milkie

Designer: Melissa Jacobson

Printed in the United States of America.

First printing August, 2014.

10 9 8 7 6 5 4 3 2 1      14 15 16 17 18

Our Commitment to Green Publishing

Chelsea Green sees publishing as a tool for cultural change and ecological stewardship. We strive to align our book manufacturing practices with our editorial mission and to reduce the impact of our business enterprise in the environment. We print our books and catalogs on chlorine-free recycled paper, using vegetable-based inks whenever possible. This book may cost slightly more because it was printed on paper that contains recycled fiber, and we hope you’ll agree that it’s worth it. Chelsea Green is a member of the Green Press Initiative (www.greenpressinitiative.org), a nonprofit coalition of publishers, manufacturers, and authors working to protect the world’s endangered forests and conserve natural resources. Organic Mushroom Farming and Mycoremediation was printed on paper supplied by RR Donnelly that contains at least 10% postconsumer recycled fiber.

Library of Congress Cataloging-in-Publication Data

Cotter, Tradd, 1973–

Organic mushroom farming and mycoremediation : simple to advanced and experimental techniques for indoor and outdoor cultivation / Tradd Cotter.

pages cm

Includes bibliographical references and index.

ISBN 978-1-60358-455-5 (pbk.) — ISBN 978-1-60358-456-2 (ebook)

1. Mushroom culture. 2. Mushrooms—Organic farming. 3. Fungal remediation. I. Title.

SB353.C83 2014

635’.8—dc23

2014015959

Contents

Introduction

PART I

The Fundamentals of Mushroom Cultivation

1. The Ecology and Life Cycle of Cultivated Mushrooms

2. The Seven Basic Stages of Mushroom Cultivation

3. Choosing a Mushroom to Cultivate

4. Choosing, Handling, and Storing Spawn

5. Cultivating Mushrooms Outdoors on Logs, Stumps, and Wood Chips

6. Cultivating Mushrooms on Compost and Livestock Waste

7. Cultivating Mushrooms on Pasteurized or Sterilized Media

8. Cropping Containers

9. Natural Pest Control and Disease Management

PART II

Mushrooms for Life: Innovative Applications and Projects Using Fungi

10. Recycling, Composting, and Vermicomposting with Mushrooms

11. Urban Mushroom Cultivation

12. Shroomin’ Off the Grid

13. Mushroom Products and Cutting-Edge Applications

14. Mushroom-Infused Beer, Wine, and Spirits

15. Mushroom Marketing

16. Fungi in the Classroom

PART III

Advanced Techniques and Research

17. Basic Laboratory Construction, Equipment, and Procedures

18. Starting Cultures and Spawn Generation

19. Storing Your Cultures

20. Advanced Cultivation and Research Strategies

21. Morel Cultivation: Research Update

22. Introduction to Mycoremediation

PART IV

Meet the Cultivated Mushrooms

The Genus Agaricus (white button, portabella, and relatives)

The Genus Agrocybe (black poplar)

The Genus Auricularia (wood ear)

The Genus Clitocybe (blewit)

The Genus Coprinus (shaggy mane)

The Genus Fistulina (beefsteak)

The Genus Flammulina (enoki, velvet foot)

The Genera Fomes, Fomitopsis, and Laricifomes (amadou and related conks)

The Genus Ganoderma (reishi and other varnished polypores)

The Genus Grifola (maitake, hen of the woods)

The Genus Hericium (lion’s mane, pom-poms)

The Genus Hypholoma (brick top)

The Genus Hypsizygus (elm oyster, shimeji)

The Genus Laetiporus (chicken of the woods)

The Genus Lentinula (shiitake)

The Genera Macrocybe and Calocybe (giant macrocybe, giant milky)

The Genera Macrolepiota and Lepiota (parasol)

The Genus Pholiota (nameko)

The Genus Piptoporus (birch polypore)

The Genus Pleurotus (oyster mushrooms)

The Genus Sparassis (cauliflower)

The Genus Stropharia (king stropharia, garden giant, wine cap)

The Genus Trametes (turkey tail)

The Genus Volvariella (paddy straw)

Acknowledgments

Glossary

Bibliography

Resources and Suppliers

For a more complete list of common names, see individual profiles for each genus

Introduction

When someone asks me if I grow magic mushrooms, I always reply by asking, Aren’t all mushrooms magical? I have been growing, culturing, researching, hunting, and learning everything I can about mushrooms for the last twenty years. I work with all kinds of mushrooms, and I am fascinated by every single one. The more you learn, the more your belief in their magic will grow.

My journey with mushrooms did not start out auspiciously. Although I loved the outdoors as a kid, I was far more interested in walking down through the woods to my grandparents’ lake in North Carolina to go fishing than in paying attention to the mushrooms growing around me. By twenty, I was living with my parents—trying to balance college classes and singing in a band—and one day my mother suggested that I stop by a nearby mushroom farm for a tour. She knew I was interested in biology, it seemed like something different and cool to do, and maybe it was her subliminal way of telling me to get out and find a job.

I knew nothing about mushrooms. Zero. Not even basic varieties at the supermarket, which in 1994 were white buttons and, newly, portabellas. But I called the farm anyway. I remember it sounding very noisy and active and the owner sounded out of breath. Sure, he said, come on by later this afternoon and I can show you around quickly if you want to see how mushrooms grow. When I arrived, the building seemed very plain, with cinder-block walls and a metal roof, and not very exciting. I wasn’t at all impressed with the looks of things.

The owner greeted me and quickly led me around, showing me the entire place, from the sterilizer unit cooking the growing media to colonization rooms and, finally, the place where the magic hit: the fruiting room. I will never forget the moment when I walked into that strange, foggy space, like something out of a dream, and down aisle after aisle of fruiting shiitake mushrooms growing on sawdust blocks. This was intriguing, and overwhelming, and I had so many questions running through my mind. My mouth opened all on its own and started peppering the owner with questions, so many that in retrospect I realize that my incredible inquisitiveness must have been annoying. But I was in shock. Amazed.

Ten minutes later the tour was over. The owner thanked me for stopping by and gave me a pound of shiitake mushrooms. I felt like I had won a miniature lottery. I walked out the farm door with my brain buzzing. It was love at first sight … with mushrooms. I sadly returned to my car and climbed in, cranked up the engine, and started pulling away when a sudden loud bang hit the rear of my vehicle. What I thought was a tire blowout was the owner of the mushroom farm, who had chased my car down the driveway and was trying to get my attention. Did I leave something there? No. I rolled down the window and asked what was going on. The owner, now panting, asked, Would you like to work here?

I often think back to that moment when the owner ran after me. If he hadn’t caught up with my car, he would have had no way to contact me. I was probably just seconds away from missing out on the future I would go on to explore with mushrooms—starting with a job at the mushroom farm. That entire tour had lasted ten minutes, but it triggered events that have lasted me a lifetime.

Over twenty years later, I now frequent food and sustainability conferences, lecturing and teaching the values of environmentally responsible, low-tech and no-tech mushroom cultivation projects that anyone can apply to their home or small farm. I am against the use of all chemical pesticides and synthetic fertilizers; I think nature knows best. Using mycorrhizae and composted mushroom substrate filled with worm castings, my gardens thrive and are highly productive without compromising the soil and water quality. I believe in creating perpetual and circular food systems, using sustainable techniques such as water harvesting and no-till cultivation, and using passive energy or seasonal production to minimize the energy use on my farm.

My work has also evolved into research, such as creating mushroom rescue modules (discussed in chapter 12) for use in regions struggling with poverty or devastated by natural disaster, where shattered habitats and cultures struggle to recover. On a recent trip to Haiti, for example, I introduced mushrooms to a group of children I met in the village of Cange. They were intrigued when I told them that some of mushrooms I had with me tasted like chicken and that I could teach them how to cultivate these wonderful mushrooms on paper or cardboard that we collected in the street. The idea that they would fruit in just a few weeks seemed magical to them. That trip was one of the most memorable I’ve ever taken. Here, I felt, mushrooms could make a real difference as a potential food source. I later returned to help set up a commercial production facility and spawn production lab to keep the process perpetuating.

Through such experiences, I’ve found that sharing what I know about mushrooms has become an imperative. Mushrooms are an excellent source of protein, and they have a wide range of medicinal properties. With an estimated 1.1 million fungi on the planet and only 150,000 collected and described (never mind being screened for their potential), you can easily see the implications for food production and medicine. In these ways fungi have the potential to shape our future for millennia to come.

This book is a compilation of knowledge I’ve gained from my experiences, from when I cultivated my first mushrooms up to the present, in which I now conduct mushroom research and own my own mushroom business. As you are reading, I must warn you that you are embarking on a path that may change the way you see yourself fitting into this life. In choosing mushrooms, you have decided to cultivate a wonderful food using what most would consider waste or by-products of many industries. I hope this book serves you well in giving you the skills necessary to explore mushroom cultivation and empowering you to dream up experiments and ideas on your own. Part skill, part art, part intuition, mushroom cultivation will give you a lifelong relationship with this incredible kingdom of life.

HOW TO USE THIS BOOK

This book is designed to help you build skill and confidence, starting in part 1 with a thorough foundation in both indoor and outdoor mushroom cultivation using purchased spawn (a form of mycelium that is physically plantable, being packaged in sawdust, grain, or a wooden dowel). Although my eventual goal is to help you become more self-sufficient by culturing and cultivating your own spawn (as well as to teach you how to grow mushrooms perpetually on just about anything), using purchased spawn will help you develop your skills and gain experience with a variety of cultivation techniques before you make larger investments of time and money. While the information in part 1 can be considered more foundational than the material in the latter parts of the book, my hope is that even more experienced growers will find value in these chapters. Rather than simply focusing on yield as an end goal, I’ve strived for a more holistic approach, one that pays careful attention to the mushroom life cycle, to ecology, to fungi’s relationships with the other kingdoms of life, and to developing the kind of intuition that will teach you more about cultivating mushrooms than a book or a workshop ever can. The focus of this book is primarily edible mushrooms, but you will find a great deal of information on medicinal, industrial, and mycoremediation applications as well. Once you develop solid cultivation skills, you can apply them to grow whatever kind of mushrooms suit your goals, or fancy.

The chapters in part 2 are designed to help you apply that foundational information to incorporate mushroom cultivation into your life and landscape, in whatever way reflects your goals. It includes information for both urban and off-the-grid growers, on making value-added products from mushrooms (including mushroom-infused beer, wine, and spirits), and the incredible and largely untapped potential of mushrooms to provide high-quality protein for people in poverty- and disaster-stricken regions of the world. part 2 is full of useful and largely low-tech ideas for bringing mushrooms even further into your life. The goal here, as in part 1, is not only to help you cultivate mushrooms successfully (though that’s a big part of it), but to help you develop an understanding of the complex relationships mushrooms have with bacteria, plants, and animals (including humans). I believe that the more we develop that understanding, the more potential we have for successful cultivation, and the more we focus on linear goals of maximum production, the more we risk failure—in more senses than one.

The chapters in part 3 cover more advanced and experimental techniques such as basic lab construction, sterile culturing, and techniques for mushrooms that are extremely difficult to cultivate, like morels. While the material in part 1 and part 2 is mostly low-tech, requiring relatively small investments in infrastructure and equipment, the material in part 3 requires more refined skill and bigger decisions. Some of it is research-in-progress, which I’ve included in the hope that as you build on your experience as a mushroom cultivator, you will contribute your own experiments and experiences to the body of knowledge about mushrooms. There is still so much to learn, and the more we understand about mushrooms and the fungi kingdom, the more we can use that understanding to grow high-quality food and medicinals, remediate polluted land and water, and replace plastics and other industrial materials with fungus-based textiles, building materials, and other consumer goods. Although many researchers and cultivators are protective of their knowledge, the only way we can really build a collective body of knowledge is through collaboration.

Don’t be too quick to rush to an advanced chapter or scale up your operation based on the information in this book. The only way to improve and succeed at your goals is to learn the specific and subtle needs of each mushroom you grow. Treat each one as an individual, like someone you know (and want to know better), understanding its individual needs and differences. This takes time and patience and, inevitably, some failure. Give yourself the opportunity to experiment before the stakes are too high. Seek hands-on workshops, attend mushroom walks, and join mushroom hunting clubs to meet like-minded people and share knowledge and experiences.

Many people have commercial aspirations for mushroom cultivation, and I have tried to include as much information as possible that can be applied to small-scale and environmentally responsible commercial operations (including a chapter on marketing your product). Again, weigh this decision carefully. Only you can decide when, if, and at what scale it’s right for you. But my hope is that you’ll have all the tools you need to scale up if you choose to.

As you proceed through the book, you’ll notice a focus on shiitakes and oyster mushrooms. This isn’t because those are the only mushrooms worth growing! I use oysters and shiitakes frequently to illustrate specific phenomena or techniques because they are two of the easiest and most satisfying mushrooms to grow, and many people are familiar with them. If you are a beginner, they are great mushrooms to start with. But if you flip to part 4, Meet the Cultivated Mushrooms, you will also find profiles of nearly thirty mushrooms, with growing parameters and suggestions for each. While most of these mushrooms are primarily edibles, some have wonderful applications for use as medicinals, in mycoremediation, or potentially in industrial capacities. Spend some time looking through the profiles and familiarize yourself with the possibilities. Although you may want to start with oysters or shiitakes, you can then apply much of what you learn to the other mushrooms, factoring in each individual mushroom’s needs.

To me, this book is much more than a cultivation guide. It is about healing the people and the planet, one mushroom and one cultivator at a time, reversing destructive cycles into creative forces. If we think with an opportunistic yet minimalistic approach, much like a mushroom, taking what it needs to survive and then returning resources to its ecosystem so they can be used by others, the future looks like somewhere I want to be. Spend as much time as possible cultivating, collecting, and observing the natural cycles of mushrooms, no matter how small they are. From old-growth forests to mulched urban sidewalks to fruiting growths on debris floating out at sea, fungi are everywhere, and there’s much to be learned from them.

PART I

The Fundamentals of Mushroom Cultivation

CHAPTER 1

The Ecology and Life Cycle of Cultivated Mushrooms

Although the ancient Egyptians are credited with pioneering the use of yeasts to create beer, wine, and bread, and historical records indicate that cultivation of many edible and medicinal mushroom species dates back over four thousand years in Japan and China, humans are not the only—or even the first—fungal cultivators on the planet. Recent discoveries have estimated that South American leaf-cutting ants have been actively culturing fungi for forty-five to fifty-five million years (Currie, 2011). In their colonies, specialized worker ants harvest and shred leaves to make a fungal growing medium. The larvae feed on the fungi; the mycelium is rich in protein and provides the ants with a natural antibiotic that helps them combat a dangerous pathogen. When a new queen rises to start a fresh colony, she carries with her a pellet of mycelium, much like a starter culture, stored in an infra-buccal pouch (a cavity in her mouth). Like this new ant queen, guardian of the mushroom spores and thus of the capacity for perpetual food production, humans too have been bestowed with the gift of mushrooms. We just need to learn to use it.

Although fungi are often somewhat neglected as a kingdom—perhaps in part because they tend to be less visible than plants and animals—they have critical ecological roles, and they interact with their environments in compelling and sometimes surprising ways. Mycorrhizal fungal relationships, for example, are obligate partnerships between plants and fungi at the root interface underground. Some examples of mycorrhizal mushrooms include truffles (Tuber spp.), chanterelles (Cantharellus spp.), and porcini (Boletus edulis). This specialized relationship allows fungi to thread into and around cell walls in the root tips, increasing the surface area within the cell and in the surrounding soil, where nutrients are absorbed and transported to the plant roots. I call this the original carbon trading scheme, where the mycelium collects a resource that the plant has a difficult time procuring and trades it for sugar, which the plant produces as a product of photosynthesis. Within these soil interfaces are countless layers of interkingdom interactions that connect bacteria, fungi, plants, and animals to maintain a dynamic microcosm of constant nutrient exchange and balance.

The tree of life is often depicted by branching, terminal ends separating organisms into distinct groups based on biological functions and, more recently, molecular data. Although many of these terminal ends seem distant from each other, a three-dimensional model would be more accurate in depicting complex relationships among organisms.

Not all fungal relationships are mutually beneficial, however. Some types of fungi are capable of attacking other living organisms, such as Cordyceps spp., which attack and mummify many kinds of insects and then fruit out of the insects’ body. Some molds, including some Trichoderma spp., are considered mycoparasites, or fungal pathogens. They possess the enzyme chitinase, which breaks down chitin, a compound found in the cell walls of fungi and various insects and soil organisms. In short, they are designed to attack and digest their fellow fungi. Many strains of Trichoderma in my collection are now being used in trials at a local vineyard investigating their ability to help grapevines combat leaf, trunk, and root pathogens. The growers inoculate the vines with Trichoderma, and the mold imparts an immune response to the plants, which then synthesize their own compounds designed for targeting a wide spectrum of fungal pathogens.

Eumycota, or true fungi—as opposed to slime and water molds, which are not technically part of the fungi kingdom—share many common characteristics, including reproduction by means of spores, a lack of chlorophyll, and the presence of chitin—a hard natural substance that provides structure and protection—in their cell walls. Fungi produce and secrete many different kinds of extracellular enzymes, such as lignin peroxidase, manganese peroxidase, laccases, amylases, and cellulases. Think of these enzymes as chemical scissors or molecular keys that cut or unlock the bonds of large molecules, such as lignin, embedded in woody plant tissue. As the mushroom’s enzymes break down its growing substrate, the smaller, essential chemical units in the substrate, such as carbon, organic nitrogen, minerals, and other trace elements, are released and are transported through the fungi’s cell walls for use as energy sources and for metabolic function.

In this process, fungal cells first stream outward into the environment—the infantry cells, as I like to think of them—and communicate back to the body of the mycelium, instructing it to produce enzymes specific to the kind of food available and what will be needed to break down those particular compounds. Fungi sweat these cell-free enzymes, meaning that the enzymes are able to saturate and move freely into the environment to degrade the organic substances before the actual fungal filaments reach them. Bacteria, by contrast, must contact their food source directly, making use of surface receptors that disassemble and transport their food source directly across their membranes. Fungi’s amazing chemical consciousness and profound ability to adapt and react quickly to the environment are part of what makes them so captivating.

Mushrooms feed in different ways on organic compounds, varying from species to species, depending on the mode of nutrition and their genetics, strains, or ecotypes. Most of what we’ll cover in this book are classified as true fungal saprophytes, or mushrooms that decompose dead organic material, such as dried plant waste. Edible but parasitic fungi, which often attack their hosts and can spread rampantly through a forest ecosystem, such as honey mushrooms (Armillaria spp.), are not covered in this text, and I discourage propagating them since they can easily outcompete most other fungi.

Cordyceps species have evolved to attack and mummify many kinds of insects, including this unfortunate wasp. Here, a fruiting body, or teleomorph, has emerged from between the wasp’s head and the thorax.

Fungi secrete metabolites that are filled with enzymes, antibiotics, and other waste by-products. Here, shiitake mycelium is sweating out metabolites (the amber-colored substance), likely as a defense mechanism in response to an environmental contaminant.

Oyster mushrooms (Pleurotus spp.) are notori ously aggressive saprophytes due to their rapid reaction mechanisms for detecting different compounds and their ability to manufacture a much wider spectrum of enzymes, not only for their own metabolic needs but also for making nutrients available for other organisms such as bacteria and plants. Other fungi are more limited in their ability to produce enzymes, reducing their capability of colonizing and fruiting from different food sources. Maitakes (Grifola frondosa), for example, can break down only very particular types of wood—mostly oak, and, in fact, certain species of oak and even certain wood densities—which limits their colonization and, by extension, your cultivation if those resources are not locally available.

Most mushrooms can be classified as either brown rot or white rot fungi based on their mode of feeding on wood-based substrates. Brown rot fungi tend to concentrate their feeding on the cellulose rather than the structural lignin, leaving behind the visually browner components of the plant tissue, sometimes cracking it into the fissure-like patterns you may see on fallen logs in the forest. White rot fungi operate in the reverse, instead focusing the bulk of their enzyme degradation on the lignin first, bleaching the woody tissue white, before feeding on the bulk of the cellulose available in the woody tissue. (White rot fungi make excellent candidates for biobleaching and for breaking down very complex man-made molecules in a process called mycoremediation.)

That’s the broad view. Of course, mushrooms feed on more materials than just cellulose and lignin. The good news—or bad news, depending on your goals—is that every strain of mushroom varies in its ability to adapt to or break down specific substances into food. Mating new strains in a lab and isolating strains from the wild offer us an infinite supply of mushrooms with differing appetites.

In fact, mushrooms prefer to vary their diets slightly. If you get to the point of expanding spawn (see chapter 18), you’ll want to adjust the fruiting formulas slightly every now and then. Otherwise your fungi may experience what’s called strain senescence—weakening of the strain due to the fact that the fungi consistently overproduce and overuse a particular combination of enzymes. Like I ask my workshop attendees, How would you like it if I fed you nothing but oatmeal for a few years? Your body would respond by manufacturing only those gut bacteria needed for that diet, reducing your microflora to a monoculture-type, rather than biodiverse, ecosystem—never a healthy model. As you develop and progress in your cultivation techniques, try to tune in to the fungal consciousness. Give your fungi what they need to survive the colonization process and for the life cycle to complete itself.

THE MUSHROOM LIFE CYCLE

Most mushrooms share the same basic stages of development, although there are a few variations and exceptions. Typically a mushroom matures and releases its spores; the spores germinate on a suitable growing media; they colonize the environment in an effort to capture as much territory as possible to build up a competitive biomass; and when the growing mycelium begins to feel confined, mushrooms fruit again. When the mushrooms are mature, they produce spores, and the cycle begins again. One of the reasons many cultivators use spawn as their mushroom starter is that it gives them a head start on the process, allowing them to grow mycelium directly, which gives them a better chance of outcompeting germinating spores from the wild.

Understanding all stages of development will help you become a more intuitive grower. You’ll learn to recognize not just the individual needs of each stage, but the specialized needs of every single mushroom you grow, so that you can develop a unique strategy for each. I spend a great amount of time observing the natural cycles of these mushrooms in the wild in the hope of catching clues from the mushrooms in their natural habitat, and I encourage all growers to spend more time collecting fungi to build an understanding of the ecological connections that trigger them to fruit.

Sporulation

Fungi produce not seeds but spores, which are microscopic packets of fungal DNA, packaged in a hard chitin coating to protect them from heat, drought, and damage. They produce the spores on the surface of their gills or pores through the process of meiosis. Meiosis is a form of sexual reproduction, meaning that instead of a cell simply dividing, with each new cell containing a complete package of DNA in its nucleus (asexual reproduction), it forms parent cells, wherein each nucleus contains just half the necessary DNA. When two parent cells combine, the new cell contains the complete DNA package (this is the same mechanism by which a human zygote is formed). So each mushroom spore carries only half of the genetic information needed for reproduction. When a mushroom is mature, it forcibly ejects its spores in a process known as sporulation.

The basic life cycle of most cultivated mushrooms includes sporulation; spore germination and cell mating; colonization; and complete colonization and primordia formation. When a mushroom matures, sporulation occurs again and the cycle repeats.

Spores can be harvested both for culturing and also to assist with identification of fungi. This spore print on aluminum foil was taken from a mature king stropharia mushroom.

Understanding spores and sporulation will be valuable to you as a cultivator. At this stage, you can collect spores from either cultivated or wild mushrooms for observation and germination by taking a spore print.

Spores germinating. Most cultivated mushrooms require two compatible spores to mate before forming a fruiting structure, or mushroom.

To take a spore print, place the stem of a mature mushroom through a slit of paper, sliding the paper up as close to the gills or pores as possible. Since you don’t always know what color the spores will be and, hence, whether they will show up best on black or white paper, it can be helpful to take your spore print on paper that is half white and half black, ensuring that the spores will show up on one side or the other. Glass is another option, as is aluminum foil, which is my preference because the spores are easy to remove from it for culturing.

Spores do not simply fall out or drop from the gill surface; when a mushroom is mature, it will forcibly discharge them—with water pressure from inside the mushroom—and will leave a pile of spores on the paper within hours if left undisturbed. Locate the glass, paper, or aluminum foil in a draft-free area to ensure a nice thick spore print.

Spores can remain viable for several years; to save them, fold the print to enclose them, place it in a plastic bag, and store in the refrigerator. The cold temperature and lack of light will keep them viable for many years with a minimal loss of germination.

Spore Germination and Cell Mating

In the case of most mushrooms, when a spore germinates, it is monokaryotic (meaning one nucleus per cell) and carries only half of the genetic information needed for sexual reproduction. After germination and sporulation, a spore’s hyphae (mycelial strands) explore its immediate environment, looking for hyphae from another germinated spore suitable as a mating strain. When compatible hyphae meet, they fuse and combine genetic material. This fusion, called karyogamy, brings together two nuclei per cell, making the cell dikaryotic. Once fused, hyphae branch out and growth explodes.

Chapter 18 describes the manipulation of this process in a lab setting. When you streak spores onto an agar-laden petri plate, those spores are in an ideal environment to mate with adjoining spores and germinate.

Colonization

Also called nutrient capture, colonization is the stage at which fungi secure their territory, competing for the nutrients in their environment. The infantry cells push their way through wood, compost, and soil until they encounter a competitor or barrier. Once that happens, the mycelium branches heavily to increase its surface area and begins aggressively digesting the substrate, recharging its biological battery in preparation for fruiting. I like to think of this process as paving a major highway; once the highway is done, the fungi begin paving all of the side roads, dirt roads, and pathways, until colonization is complete.

Complete Colonization and Primordia Formation

The fruiting cycle begins—stimulated by environmental changes and nutrient availability—when colonization is complete and the fungus feels threatened enough to put its energy into a structure that will produce spores—mushrooms! Nutrients and water from the captured biomass stream to spots that the mycelium has chosen as good fruiting locations, based on favorable gas exchange gradients, consistent humidity or access to water, and the availability of light. Primordia, which resemble little knots, are the first observable sign that mushrooms are starting to fruit. The fungal life cycle comes full circle when a mushroom matures and releases its spores. At that point, the spores are free to explore the world in search of a mate and a new home to set up a colony.

During colonization, the mycelium fans outward to capture nutrients.

Mushrooms form when colonization is complete. Here, king oyster (Pleurotus eryngii) primordia are fruiting on sawdust.

The mushroom life cycle is complete and will begin again when a mushroom produces and forcibly ejects spores. Spores are adhesive when they are discharged and sometimes stick together to form long chains, as with these oyster mushroom spores.

FUNGAL METABOLISM: BY-PRODUCTS

In the process of this life cycle, what do fungi require for food and what are the metabolic by-products? For food, fungi simply require a carbon source, or a feedstock—wood chips, sawdust, coffee grounds, agricultural wastes—which they break down using their digestive enzymes. Since they’re essentially sweating these digestive enzymes into the environment, I like to think of fungi as humans turned inside out (even though this isn’t even close to being biologically correct). Instead of eating food, digesting, and then excreting waste, fungi excrete enzymes into the environment, which digest their food using oxygen, and then the fungi absorb the resulting dissolved nutrients directly through their cell walls. The fungi then excrete and essentially swim through their own waste as it accumulates. The by-products, just like our waste, are toxic to the fungi and accumulate in their immediate surroundings, so the mycelium must also secrete other secondary enzymes and by-products that attract and encourage bacteria that recycle the waste into substances less toxic to the fungi.

Mushrooms need oxygen to develop correctly. Elevated carbon dioxide levels can influence the shape and length of the stems in most mushrooms. Here we see oyster mushroom primordia stretching in a fruiting room with poor ventilation and therefore excessive carbon dioxide.

Chicken of the woods (Laetiporus sulphureus) mycelium grazing on methicillin-resistant Staphylococcus aureus (MRSA).

Like animals, fungi produce heat, carbon dioxide, and water, in the form of metabolites. For this reason, they are the perfect biological companions for the plant kingdom. In fact, integrating mushroom cultivation with enclosed plant production systems such as greenhouses can improve growing conditions for both sets of organisms.

Heat

Fungal enzymes produce heat when combined with available oxygen. The enzymes cleave molecules into smaller and smaller compounds, resulting in the bioavailability of smaller chains of cellulose and other energy-rich compunds as food sources. Much like in our stomachs, temperatures increase due to the spike in digestion or breaking down of the food source into usable material. This temperature increase, though slight, is relevant because you’ll need to account for it when you’re planning your growing space; packing too many mushrooms together can overheat and cook the mycelium during colonization, creating large dead pockets and anaerobic zones where molds and other thermophilic bacteria will thrive. These bacteria and molds will marble the growing medium with unused volumes of substrate, decreasing yields and increasing your risk of other containers nearby becoming infected. Monitor and moderate the heat levels and you will not have any problems.

Carbon Dioxide

As fungi consume the growing medium, they release enzymes and stimulate the combustion of oxygen, which creates and releases carbon dioxide. Much like humans, mushrooms need fresh air constantly, especially when they are forming actual fruitbodies. Excessive levels of carbon dioxide result in stem elongation, an undesirable result for growers because caps are typically more valuable than stems.

Since carbon dioxide is heavier than oxygen, when a fungus excretes it, the gas pools in undisturbed pockets of soil and depressions. These invisible pockets of carbon dioxide cause developing mushrooms to stretch, staying very narrow with a reduced cap size, which helps them navigate up through duff in the forest, or through straw or wood chips in your garden. If mushrooms formed large caps early in their development before having the chance to push through these barriers, they would not be able to release their spores effectively into the wind. Because spore dispersal is critical to mushroom survival, some mushrooms have developed other adaptive mechanisms to help them disperse spores. Truffles, for example, evolved to rely on insects and animals for spore dispersal.

Other By-Products

Every fungus is chemically unique, and the discovery of new compounds that fungi produce is rapidly increasing their use in many applications and industries. These compounds can be found either embedded in the mycelium or floating about in the sea of fungal metabolites. Fungi produce these different compounds in varying amounts in reaction to environmental changes and shifts in their available food sources. An observant cultivator can customize the growing parameters to optimize the levels of desirable by-products.

FUNGAL GROWTH: REQUIREMENTS

Mushroom cultivation is not difficult if you can tune into the natural growing requirements and try to re create what natures seems to do so effortlessly. Whether your mushroom cultivation projects are located indoors or outside, there are four key components that comprise the essential needs of a mushroom to produce prolifically; they are food, water, gas exchange, and light. If any one of these variables is missing or neglected, the mycelium and mushroom biomass suffers greatly, so perfecting the subtle differences within each one of these factors for every mushroom species is your goal. This is a constant learning process until you perfect it, so be patient while mastering these requirements below.

Food

Fungi are heterotrophs, or consumers of food just like animals; however, mushrooms have adapted their enzymes to break down complex organic compounds found in their habitats such as logs, leaves, straw, manure, and much more. Many mushrooms prefer wood and plant debris as their main food source, while others consume manure-based substrates. I typically classify mushrooms into two categories when it comes to cultivation, the primary decomposers and the secondary decomposers. These classifications help a cultivator design a production system based on sequencing the growth of specific mushrooms first on one food source, then adding a second species of mushrooms when the food source has been altered or decomposed. Supplements can also be used in bulk-growing medium formulas; however, the more you use, the higher the risk of contamination competing with the mycelium for the prime real estate, so use supplements sparingly or not at all. Most supplemented media are used in sterilized substrates, which is easier to control for contamination since the media are autoclaved and spawn transfers are performed in a sterile environment.

Water

Mushrooms need high moisture and humidity levels (90 to 95 percent) to sustain their growth and supply the mycelium with enough water to spread into the environment. The sweating of enzymes lubricates the paths of the spreading mycelium, allowing it to swim through the growing medium, even when conditions are relatively dry. In this respect, fungi can breathe in humid air, condensing it into water internally in their cells, and redistributing the water wherever the body of mycelium needs it most, whether for nutrient capture or for mushroom production efforts. Once the colonized growing medium has charged its mycelium full of nutrients, it is ready and waiting for a good soaking, where the water pressure generated by some fungi can actually break through concrete and asphalt, an amazing feat for a compressed bundle of mycelium!

Hydraulic pressure can force mushrooms up through concrete, asphalt, and heavy gravel.

Be aware that mushrooms can hyperaccumulate heavy metals in tissue, so be sure to test the water you are using for lead, mercury, and arsenic, at the minimum, to make sure the fruiting bodies are not going to be toxic. City water, although resplendent with chemicals and chlorines, is usually not a problem for mushrooms and is fine to use, but I still recommend testing any water source no matter how clean you think it may be, including pond, well, and roof-reclaimed water sources.

Gas Exchange

It must be understood that when mushrooms are colonizing, they are embedded in wood, under mulch, or streaming through compost piles, with very little oxygen needed until they are ready to fruit. The entire biomass uses the outer edges of the mycelium, in contact with fresh air, transporting oxygen deep within and channeling carbon dioxide out. If no oxygen is present, or if the medium is too wet or deep, the mycelium may not be able to supply enough oxygen to its entire body, creating dead zones. Mushrooms form where oxygen is plentiful, and will emerge from the fruiting medium wherever there is access to air, such as a tray surface or holes in plastic bags and buckets. Keeping mushrooms too wet during fruiting can drown them, by coating them with a continuous film of water; their mycelium cannot breathe

One day later, these Coprinus mushrooms have pushed through an asphalt driveway in the completion of their life cycle.

The colonization room should have less oxygen than a fruiting room to trigger the natural stimuli that mushrooms need for prolific fruitings; most commercial farms keep colonization rooms at around 5000 parts per million (ppm). When colonizing mushrooms in bags on a small scale, it is possible to use the same room for fruiting, though this is not ideal since diseases can spread to uncolonized media.

Fruiting rooms by comparison should be ventilated at all times to carbon dioxide levels below 1000ppm; this promotes primordia formation and avoids stem elongation. Adding plants in growing rooms is a great idea to help offset carbon dioxide.

Light

Don’t all mushrooms grow in the dark? Actually, only a small handful of species—including the Agaricus species (portabella, white button, et cetera)—can mature and develop true to form in the absence of light. All other mushrooms require diffuse natural or fluorescent light. For a cultivator, the wavelengths that are most important are in the blue-green spectrums. They are responsible for metabolic pathways that regulate most energy and growth requirements for mushrooms, as well as initiating mechanisms for creating higher levels of protein, vitamin D, and medicinal properties. This allows low-wattage LED lights to be used in a fruiting room to save energy.

Most mushrooms need light to prevent stem elongation and to develop cap cuticle color. These golden oyster (Pleurotus citrinopileatus) fruiting blocks were both initiated at the same time. The one on the left was left in darkness, and the one on the right in natural, diffused light. Fungi also use different wavelengths of light to synthesize vitamins and medicinal compounds.

For most edible mushrooms, a lack of light creates the same effect as elevated carbon dioxide conditions: long stems and small caps. Mushrooms stretch from those dark places underneath mulch and in depressions, their caps small and narrow, enabling them to weave upward and into a well-lit environment. Mushrooms are also phototrophic (turning toward light), and they are capable of utilizing ionizing radiation from sunlight for the manufacture of many chemical compounds, including vitamin D and melanin, similar to the processes in human skin. This means that a mechanism exists that allows fungi to react and use radiation for their survival and biochemical triggers, a strange phenomenon since they lack the pigment chlorophyll, the pigment plants use for that purpose. This fungal production of chemical by-products has important implications for humans; by discovering new ways to cultivate mushrooms, we are