Cultivating Mushrooms
This article discusses the cultivation of some edible and medicinal mushrooms. Some of this material appeared as the latter half of “All About Mushrooms”, published in the August-September 2010 issue of Mother Earth News. Added to the site January 28, 2013.
Note: I recommend that you click on the thumbnails on this page. To accompany some of the called images, I added a good deal of additional information and advice not included in the text.
In “Fungi in the Homestead and Farm Ecology”, I sketched the functions of fungi in the ecology and some roles they can play in a sustainable homestead or farm. Now let’s look at the basics of cultivating a wide range of edible and medicinal species. For more information and sources of started spawn, see “Resources for Working with Fungi”.
Please bear in mind that some mushroom species are lethally toxic, so it is essential to know your mushrooms when bringing them to the table, whether wild or cultivated. Some cultivated species such as shiitake and oyster mushrooms are easy to identify on the logs in which we have inoculated them. A species like Pholiota nameko, however, is a close enough look-alike to the deadly Galerina autumnalis to require as careful identification of mushrooms on cultivated logs as for those gathered in the wild.
Starting with Spawn
Remember what was said in “Fungi in the Homestead and Farm Ecology” about the hazards the fungus encounters as soon as it sprouts from the spore. In the wild, fungi get past these threats by the sheer mass of spores produced—billions per mushroom. Vast numbers perish, though a lucky few survive and thrive. But the math doesn’t work when we want to cultivate mushrooms—we have to give an edge to the germinating fungus. Doing so requires near-sterile growing conditions—conditions not easy to produce in the homestead environment without special equipment and a dedicated “clean room,” an environment protected from bacterial and fungal contaminants. Most homesteaders choose to leave the heavy lifting of starting spores in sterile cultures (and cloning tissue from selected mushrooms) to specialists able to create such environments. Once the mycelium started in these special conditions has its defenses robustly in place, it can be grown in media like sawdust, wood chips or wooden dowels, cardboard, even burlap sacking and natural fiber rope; and it is this started “spawn”—far less vulnerable to threats from the environment—that we can buy for growing fungi in the homestead.
Of course, if we get more drawn into the fascinating world of fungi, we might want to set up a simple clean room of our own. It is also possible to transplant mycelium of identified wild species into compatible substrates in the homestead. For other approaches to starting fungi using more natural, homegrown methods, see Paul Stamets’ Mycelium Running, listed in “Resources for Working with Fungi”.
Spawning to Logs
The natural “menu” of the various species will determine to a large extent what substrate we use to grow a species—that is, what organic materials we inoculate with spawn to grow mushrooms for our use while speeding decomposition of the materials to soil.
There are many species that are “wood lovers”—who feed on dense woody tissues such as fallen trees. Of special interest are those that colonize recently-dead trees still standing, a premier example being shiitake (Lentinula edodes), one of the first mushrooms cultivated commercially in this country other than the supermarket “button mushroom” (Agaricus bisporus).
Growing Shiitake
Since shiitake colonizes recently-dead trees rather than those on the forest floor well into decomposition, we cut our shiitake logs from living trees—the best choice being young healthy trees that need to be thinned anyway, so that harvesting these logs leaves the forest invigorated rather than depleted. Most hardwoods make excellent substrate for growing shiitake—oaks are generally considered the best of all. The size of the logs is determined by the dimensions of the tank in which they will be soaked, and by what we can lift out of the tank without straining the back. I like to use logs from two and a half inches in diameter, up to five or six inches, and two and a half up to four feet long.
I cut logs in the dormant period only—late winter is best, before the sap starts to rise. Tight, persistent bark helps protect the growing mycelium in the inoculated logs from contamination by bacteria and competition from “weed” fungal species. Bark on a log cut after the sap has begun moving in the cambrium will tend to slough off, leaving the mycelium exposed.
I might cut my logs in mid-February (Zone 7a), then allow them to rest for about a month. About mid-March (up to late April or so), I drill numerous holes in the logs, and “plug” the holes with spawn, which I buy from a friend and mushroom mentor with the experience, equipment, and clean room to start it from spores or cloning techniques. The spawn might be in the form of either sawdust or wooden dowels, in which shiitake mycelium is actively growing.
After plugging the logs, I daub the plugged holes with melted wax to seal the spawn and prevent its drying out, which might kill the mycelium. (Some growers use plugs of foam plastic to seal the holes. I find the sealing wax more effective, and I don’t like the generation of plastic waste.) I then rack the prepared logs out of contact with the ground, in crisscrossed ricks on wooden pallets. Now, patience—the spawn run or incubation period can take a whole year, meaning harvest begins the following spring. In the driest part of summer, I put the sprinkler on the logs for twenty minutes or so, about as often as I feel the need to water the garden.
Note that the more generous I choose to be with the spawn (the more holes I drill and plug), the shorter the incubation time for the logs, and the earlier I can expect a harvest. (This year I spawned generously with a strain that is unusually precocious, with the surprising result that the logs started spontaneously fruiting with the early fall rains.)
Shiitake is dormant in the winter, but during the rest of the year, the logs can be “fruited” (induced to grow mushrooms) by soaking them in a tank, imitating for the fungus a prolonged period of rain, which in a natural setting would trigger mushroom (spore) production. Soak time depends on the condition of the logs and how dry the weather has been—from overnight up to a couple of days. After the soak, I rack the logs with enough space to allow growth and easy harvest of the mushrooms.
After a couple of days, tiny mushroom buttons start forming, most likely at the inoculation sites. From that point, the mature mushrooms grow with amazing rapidity, so I monitor frequently and harvest before they become over-developed. Ideal time to harvest is just after the veil covering the gills has pulled away from the stem, but while the cap’s edges are still “incurled” rather than flattened out (as shown on the right). I cut the base of the stem flush with the surface of the log, leaving no stub of tissue prone to infection.
After fruiting, a log needs about six weeks recovery, while the fungus digests more of the cambrium and softwood tissues to store energy and prepare for another round of fruiting. For a steady supply of mushrooms, therefore, I divide my total number of logs by six, and fruit one batch per week.
Managed as described, shiitake logs will produce harvests for about four years.
Growing Other Species on Logs
Photo courtesy of Sharondale Farm
We have been growing shiitake for many years. More recently, we have been experimenting with other species that can be spawned onto logs: oyster mushrooms (Pleurotus ostreatus), a particularly aggressive and promiscuous species that can be spawned to many woody substrates, including those of “weed” trees like Ailanthus that make poor firewood, or to straw; reishi and turkey tail (Ganoderma lucidum and Trametes versicolor), medicinals which can both be spawned to the same log; maitake (Grifola frondosa), a large, delicious edible considered to have beneficial medicinal qualities as well; lion’s mane (Hiricium erinaceus), one of the few fungi that can be spawned onto black walnut; and Pholiota nameko, which as said requires care at harvest to avoid toxic look-alikes among Galerina spp., Hebeloma spp., and other toxic species that grow on wood. All the above species do best on hardwoods, but it is possible to cultivate a few—for example chicken-of-the-woods (Laetiporus conifericola)—on logs cut from conifers.
Note that many of these wood-loving species are not typically racked, like shiitake, but are often laid right on the ground; half buried horizontally in “rafts;” or even buried vertically one-third their length in the soil, “totem” style. Logs managed in this way are usually not soaked—we look for harvests in their proper season, especially following a good rain.
Stumps and Slash
Note also that wood-loving species, including shiitake, can be spawned to the stumps that remain after forest thinning. The wicking of moisture up from the roots into the stump helps support the growth of the fungus, eliminating the need to soak; and the fungus helps break down the stump without bringing in heavy, expensive grinding machines to do the job.
A fascinating way to inoculate wood-loving species like oyster mushroom is to replace the lubricating oil in a chainsaw with vegetable oil infused with a heavy load of spore (mycospored oil), so every cut of the saw leaves behind countless spores. If the slash—discarded tops and branches—is cut up enough to ensure close contact with the ground, the fungus may establish and thrive on it and the stumps, yielding harvests of tasty mushrooms while speeding decomposition.
Spawning to Other Substrates
Saprophytic fungi consume a wide variety of dead plant materials, from livestock manures (undigested residue of plants) to stems of annual plants to dense cellulosic materials like wood. We can choose among many species, to spawn to the type of organic debris we need to assist in their return to earth.
Some cultivated species in this group can be spawned to pasteurized straw, or to leached, pasteurized cow manure. But let’s keep the focus on species more easily cultivated using natural, low-energy homestead methods.
One of the most useful and easy to grow—and delicious—of the mushrooms in this group is Stropharia rugoso annulata, commonly known as garden giant and king (or wine cap) stropharia. This past spring I started a patch of stropharia in my asparagus beds. The rapid breakdown of the mulches on the beds nourishes the asparagus (a heavy feeder); which aids the fungus in turn by keeping it cooler and more humid, in the dense shade of its mass of fronds.
Along an interior edge of my two asparagus beds, I scraped away all mulch to reveal the soil surface, which I covered with a layer of clean, perforated, soaked cardboard. I then interspersed layers of fresh wood chips (from a crew that was clearing electric lines) and a gallon of started stropharia spawn (from my mushroom guru), topping off the inoculated chip bed with another layer of soaked cardboard. Finally, I covered the stropharia patch (and the entire asparagus beds) with clean straw, free of mold or other contaminating organisms, and gave the patch a final soaking.
Photo courtesy of Sharondale Farm
After a couple of months, there was vigorous growth of white, stringy mycelium through the chips. The rains of early fall brought on a couple of modest flushes of delicious mushrooms, which occurred not only in the inoculated chip bed, but in the straw mulch into which the mycelium had spread. Production should be greater next year, especially if I continue to feed the patch with fresh substrate—either fresh chips when I can get them, or more straw as a mulch.
Addendum January 2013: I have found such inoculations of wood chip beds over soil more challenging than growing shiitake and oyster mushrooms on logs. I have found it easy enough to establish the bed initially, but have not successfully kept one going from one year to the next. I’ll be trying again this year and make a later report. ~HU
Other edible species compatible with wood chips, cardboard, and/or straw include oyster mushroom, elm oyster mushroom, parasol mushrooms, and Agaricus subrutiliscens.
Every gardener knows how difficult it is to compost woody debris like prunings, or high-cellulose corn and sunflower stalks, in a standard compost heap, and such “wastes” are all too frequently sent off to the local landfill. The ideal mushroom to break down complex debris heaps of these materials—plus autumn leaves, lawn clippings, etc.—is the Blewitt (Lepista nuda)—a beautiful pale lilac, edible mushroom.
Some mushrooms are “dung lovers,” growing in manure heaps, composts, and heavily manured soils. One edible species that is easily cultivated on such substrates is the shaggy mane or Coprinus comatus (from the Greek word copra, or dung).
The Wild Enters the Garden
Finally, remember that—if you begin maintaining mulches or pathways of wood chips or other organic residues, as in an “edible forest garden”—you will begin seeing a host of mushroom species emerging in them. Even unidentified “little brown mushrooms” will be doing the important work of converting the mulches to soil fertility. Some, however, will be friends such as Blewitt (Lepista nuda) or wine cap stropharia, which can be harvested for the table—a case of “reaping where we did not sow.” (I have found both these species volunteering here and there since I started maintaining such permanent mulches.) As always when gathering wild mushrooms, proper identification is absolutely essential.
Photo by Archenzo on Wikimedia