Cultivating mushrooms in natural logs

How to grow shiitake mushrooms and make money doing it. $50 Half-day course begins with brunch: 11 am to 3 pm. Instructors are Albert Bates and Frank Michael.

 Course Overview

Selection and Cutting
Select and cut trees for mushroom cultivation anytime between the time leaves turn brown in the Fall to a few weeks before leaf-bud in the Spring. Any of the oaks are best (except for blackjack), with good yields from hornbeam, ironwood, hard maple, and sweet gum. Other species yield less mushrooms, and the softwoods yield none since their aromatic resins are fungicidal. The bark should look healthy, without trunk rot or leaf blight. The logs should have medium thick bark; handle them gently to preserve the bark as a barrier to other fungi. A good size for logs is 2" - 6" in diameter and 40" long. Firewood cutters or farmers can meet your requirements for about $0.75/log.

Inoculate within three weeks of cutting. Delays can result in lower yields from the logs becoming too dehydrated and colonized with other microorganisms. If you cannot inoculate you logs right away, first make sure the bark is dry, and dead-stack them like firewood over two horizontal logs off the ground in a shady spot, and lightly cover them with plastic to keep off the rain. Rain on the logs reduces drying, but accelerates rotting. Tight wrapping of the logs with plastic produces wet bark from condensation; leave the ends open to air.


Place two boards, 10'x2"x10", flat on a pair of sturdy sawhorses. You'll need a hot plate, an old pot, and half a sponge cut lengthwise to apply the melted cheese wax. A high-speed drill makes life easier for runs of over 100 logs. Use a 5/16" diam. bit for plug spawn, or 7/16" diam. for sawdust spawn, with a drill stop set at 1" depth for plugs, 3/4" for sawdust. When using sawdust spawn, an inoculating tool will keep your fingers from wearing out. Put the spawn in a plastic bottle-bottom inside a tool pouch, and have the aluminum tags in another pouch with some 1" roofing nails.


Inoculation can be done by one person, but is more efficient and fun with a crew of three or four. Load a few logs onto the sawhorses. Start 2" from the end of the log, drilling a pattern of holes 6"-8" apart along the log, and 2"-3" around the log. When done roll the log to the next person, who taps in the spawn plugs in with a hammer so each plug is flush with the bottom of the bark. When using sawdust spawn, jab the inoculating tool 2-3 times to pick up a slug of spawn. Place the end of the tool on the hole and squeeze out the spawn with your thumb, packing the hole to the bottom of the bark and knocking off any excess spawn. After checking that all holes are inoculated, roll the log down to be waxed. A thin coat of hot cheese wax is dabbed once over each inoculated site using the sponge. Several holes can be done from one dip of the sponge, but when the wax stops bubbling around the hole, it has cooled too much and it is time to recharge the sponge, and perhaps plug in the hot plate again. Do not let the wax get too hot, since the smoke can flash into a fire. Finally, a single roofing nail holds down an aluminum tag at the end of each log, on which you can write down the date and strain of mushroom with a ballpoint pen or a color-coded paintstick.

Spawn Run
Stack the logs in a shady, sheltered spot. If necessary, use 60% shade cloth, the tough woven kind that will not tear when dragged over logs. Initially stack in a dead pile over horizontal logs and cover loosely with plastic to keep the rain off while retarding evaporation. The logs are well-hydrated with fresh sap for the first two or three months, but after that, moisture-loss becomes excessive. The logs are then restacked to allow periodic soaking-and-drying during the remainder of the 9-month spawn run. The lean-to stack is our favorite: lay one log down on the ground, then lean three logs against that log, leaving one log-width between them. The more windy or dry the location, the flatter the logs are leaned. Place another log hori zontally over those three logs, and on top of it stack three more logs as before, but staggered so each log is lying over the gap between the logs underneath (so the logs don't rain-shadow each other). Continue stacking logs in this way. Ideal stacking locations are shady, wind-protected, and moist, like north slopes. In Winter when the leaves are off the trees, 60% shade cloth, burlap bags, or pine boughs may be needed. Evergreen trees make an ideal cover. The most common cause of failure to produce mushrooms is the moisture inside the log dropping too low, causing the mycelium to be stunted in its propagation, become stressed and contaminated, or die from dehydration. You need to soak your logs using a sprinkler during the spawn run, every day in dry Summer spells. However, it is very important to ALLOW THE BARK TO DRY BETWEEN SOAKINGS.

If the bark stays wet continually, fungi and bacteria in the bark prosper, while the mushroom mycelium in the log declines. Some contaminants can be endemic even in healthy-looking logs. One example is little black cankers of Bulgaria iniquans, which become blackish jellylike cup fungi, but are harmless and allow near-normal crops of shiitake. Other competitors decimate shiitake, like the forest-green fungus Trichoderma, or Diatrype stigma, a pearly-gray turning-to-black bark-blowoff disease. In all cases, prevention is best - if you start with healthy trees and manage your logs carefully, you will minimize any problems and have good mushroom crops off the same logs for years.

At last, harvest is near! The spawn run requires at least one warm season for shiitake, oyster, and other log-grown mushrooms. One exception is the cold-weather fruiting shiitake strains, which take about a year and a half before the first fruiting. Fruiting is near when white splotches of mycelia appear in an irregular white ring at the ends of the logs. Mycelia will not colonize dry ends of the log, though the logs may be ready. It is wise to allow plenty of time for the spawn run before attempting to force-fruit the logs. Precocious fruiting stops vegetative growth, with mediocre yields resulting. A good strategy is to let nature take her course, allowing the first couple of harvests to occur naturally as Fall or Spring rains thoroughly soak the logs. The first small flushes of mushrooms will appear in those logs that are ready to support them. Thereafter, you can choose to let Nature continue to fruit the logs with a minimum of management (mostly an occasional soaking in hot, dry weather), which will give you lots of mushrooms in the Spring and Fall, and very few or none in the Summer and Winter. The alternative strategy is favored by commercial cultivators, for whom reliable week-in, week-out supplies of mushrooms bring the highest prices from chefs and produce managers. This strategy is described next.
Continuous, year-round cultivation
When a fully incubated log is immersed in clean water a few degrees cooler than the ambient air (tap water usually is) and soaked for 24 hours, this combination of extra water and cold simulates the stress of Spring and Fall conditions. The log begins to fruit within one or two days, and harvests continue for 7 to 10 days. Mushrooms are harvested at least once a day, when their caps are about 80% unrolled. Cut the stem flush with the bark with a sharp knife, and store in a cardboard box at 36-41° F for up to a month (however, most discerning chefs will buy only those harvested the same week). After a few days, pinning gradually tapers off, and the logs need time to digest more wood for the next fruiting. In this resting (digesting) stage the logs are dead-stacked in a warm place and allowed to dry slowly. Too much drying can kill the mycelia, but allowing rain to soak the logs will cause premature fruiting, resulting in wasted labor from inadequate harvests (and contamination from wet bark if the logs are dead-stacked). Mycelia (and mushroom fruiting) becomes dormant when the average temperature approaches the low 50's.

 For year-round production, logs to be fruited in Winter and Spring need to be rested indoors, since mycelia does not feed while it is dormant. The optimum resting period for harvest rate is about 8 weeks. Divide the logs into stack sizes to fit the soaking tank (a 150-gal. stock tank is hose-filled, holds 20+ logs). Number the stacks, and keep a log of soak dates, yields, strains, etc. Rotate the stacks through the soaking tank for weekly harvests. The best sale prices are obtainable for reliable, high-quality weekly deliveries. To reduce heating expenses, fruit wide-range and cold strains in the cold months and wide-range and warm strains in the hot months. A book detailing these strategies is Growing Shiitake in a Continental Climate by Kozak and Krawzick, as part of our Mushroompeople Commercial Kit.

Frequently Asked Questions

Why do we focus so much of our efforts on shiitake?

In a word, health. While other mushrooms have strong associations with good health, and some are even stronger immune boosters (maitake, for instance), few are as easy to grow, forgiving to beginning growers, or adaptable to different climates as shiitake.

In Japan in the sixties, shiitake sales flattened out after two strong decades of growth. What changed the situation in Japan in the sixties and led to their enormous production (and consumption) of shiitake today? In a word, health. In the sixties, Japanese consumers became more concerned about their health, and, at about the same time, the medical research on shiitake's phenomenal benefits began coming in.

Today those benefits are well-documented. Shiitake's powerful immune-boosting action reverses the T-cell suppression caused by tumors, making it a valuable ally against cancer, leukemia, lymphosarcoma and Hodgkin's disease. Antiviral actions, due to substances present in spores and mycelia, inhibit cell division of viruses, impeding the spread of flus and other infections. One shiitake mushroom, eaten with a tablespoon of butter, actually reduces serum cholesterol. In Japan it is taken to prevent heart disease because it regulates both high and low blood pressure. As an anti-inflammatory, it improves stomach and duodenal ulcers, neuralgia, gout, constipation and hemorrhoids.

Shiitake also counteracts fatigue, generates stamina and improves the complexion. So that's the story of Japan's success, and why it is likely to be repeated, irrespective of what the price of mushrooms is, or what growers do or don't do to improve their marketing. It's just a matter of time. This is a food the world wants.

What do I need to grow Mushrooms?

Many people are afraid to begin growing forest mushrooms because of early childhood associations of mushrooms as poison. When you cultivate particular mushrooms however, you know what to expect and are not likely to confuse what comes up with something else that is not good for you. Shiitake, with its cracked, fleshy top--deep brown in the center and lightly misted with white flecks at the edges--is difficult to confuse with other oak-dwelling mushrooms.

How does one learn about growing mushrooms?

The traditional ways are to attend a workshop or grower association event, to read books and articles, or to talk with experienced growers. The newest, and easiest, way is to buy or rent a videotape. That is why we produced Mushroompeople's Masters of Modern Shiitake series. Many of these tapes have been reviewed in The Mushroom Growers Newsletter (contact: for back issues).

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