CA Mushrooms

Morel Cultivation for the Adventurous and Observant

by Terri Marie Beauséjour
Copyright 2000, all rights reserved.

This article first appeared in Mushroom: the Journal of Wild Mushrooming. Subscriptions are $25 for four quarterly issues from Mushroom the Journal, 1511 E. 54th St. Chicago, IL 60615.

As the Bay Area hills are suddenly ablaze with the dazzling golden-orange of California poppies, stunningly contrasted by the azure-blue lupines and brilliant lemon-yellow wild sorrel, I realize that, in what seemed like a blink of the eyes, our cool, wet winter has been supplanted by what can only be characterized as -- summer. And it's not even April yet! But northeastward, in the Sierra Nevada, the spring season has just begun, and spring in the Sierra means it's time to start the treasure-trek for morels.

Morchella © Michael Wood
A Wild Morel
Photo © Michael Wood

In Northern California, the process of searching for morels differs somewhat from that of our eastern and northern friends, who have the good fortune to know of and depend on perennial "secret spots."

In the Bay Area proper, it seems the soil temperature doesn't get cold enough and the spring humidity doesn't last long enough to allow for many reliable, seasonably-induced fruitings. Thus, we must rely on certain "catastrophic" events to trigger the massive fruitings we crave, and each year, the search begins anew.

Qualifying events include:

  1. Forest fires
  2. Controlled burns
  3. Logging and undergrowth clearing
  4. New landscaping

While finding morels in newly landscaped areas requires no more advance planning than driving about looking for fresh woodchips sporting morel fruit-bodies, the big adventure begins with a few advance trips to this year's collection of potential burned and logged sites. These can be found on maps obtained from the U.S. Forest Service and the California Dept of Forestry and through communication with the all-important network of fellow morel enthusiasts.

I recently heard it said that Larry Stickney's cue to begin looking for morels is two 80-degree days in a row. It is now the last week in March, and this week we had just such a pair or days. So, armed once again with our compasses, maps, raingear, whistles, altimeters, soil thermometers, H2O and Powerbars, we will set the alarm for 4 a.m. to hit the road and head for the hills before sunrise.

We will begin at the lower altitudes, say 3,000-4,000 ft, then proceed increasingly skyward through April, May and often into June as springtime conditions move to the higher elevations. As we refine our understanding of the habitat of morel fruiting, we are better prepared to hone in on the right location at the right time, throughout the progression of the season.

Of course, at the forefront of our minds, by virtue of strong cues from our fresh-morel-deprived senses, is the hope of hitting the "big bonanza" to rival some of the legendary finds of yore. But some of us have ulterior motives. The "catastrophy-induced" conditions we discover offer an opportune window into nature's laboratory, and we aspiring morel cultivators ought not miss this chance for observation and enlightenment.

Take, for example, soil temperature. A few years ago we set out to test the theory that morels tend to fruit within a fairly narrow range of temperatures -- it was thought between 10 and 15 C. So we have taken to toting a thermometer with a long probe rod to readily test the temperature between about 2 to 5 inches of soil depth.

We tested numerous likely spots where all other known conditions appeared "right", and also tested places where morels were actually fruiting. Our results seem to have verified that indeed, in locations with soil temperatures colder than 10C, we did not find fruiting bodies, whereas the tested locations with fruit-bodies were within the expected range.

Since morels are known to favor fruiting in "disturbed" areas, we often investigate both logged areas and burned areas -- both disturbance types have usually been created the previous summer and fall in our forests. It is understood that these events cause a massive release of nutrients that are useful for the growth of morels. With the spring rains and snowmelt, the nutrients are absorbed into the soil, triggering germination of the overwintered sclerotia, and providing a source of nutrition for rapid mycelial growth, possible plasmogamy, and formation of new sclerotia, some of which, given an appropriate microclimate, will produce the ever-sought fruits.

© Fred Stevens

Urban Morels in a landscaped area. Photo © Fred Stevens.

The "right" microclimate will be one that has acceptable levels of soil moisture, air flow, air temperature and humidity. Observance of these parameters in "nature's lab" will help us to derive and verify growth parameters prescribed for our cultivation projects at home.

For example, in colder, wetter environments, the morels tend to fruit in more exposed areas, such as upon ridges or on warmer slope facings, along roadsides and in areas with less canopy cover. In warmer, drier weather they are found tucked in under logs and other woody debris, down in burnt-out stump holes, shallow depressions, along rivulets and creeks, and under young trees and shrubs.

This suggests that the organism is quite sensitive to these above ground conditions, and will adapt and pinpoint particular spots in which to position its fruits.

This year, I intend to gather more specific detail, evidence to help either lend support to, or expand upon known growth parameters for the Morchella species we find. By the time you read this summer issue, we will probably have both filled our bellies and our jars with the bounty of another spring, and should be ready to take what we have learned in the field and apply it to some cutting edge cultivation projects at home.

Starting cultures

Hopefully, you have already collected several cultures from fresh fruit bodies and/or spores. The mycelia are showing healthy growth in your tubes or plates, and have possibly begun to form "micro-sclerotia". (Micro-sclerotia is a term coined by Paul Stamets.) If in creating your cultures, you happened to introduce fragments of mycelia from two colonies of the same species, you may observe an area of "mycelial meld", characterized by a ridge of hyphae forming at the juncture where growth from the two colonies meets. This may be followed by deposits of brown pigment into the medium directly below this ridge. Less often, the two colonies will each proceed radially to the outside of the media surface with no merging at their junctures. The culture may eventually form small white to rust colored masses of "micro-sclerotia."

Morel Life Cycle

Morel mycelia tend to exhibit rapid growth on agar media, and to readily form sclerotia in sufficiently nutritious substrates. Research has shown that the formation of sclerotia is a key component to both the survivability of the morel organism under harsh conditions, and to its fruit-body production.

The organism can cycle repeatedly through the mycelial growth, sclerotia formation phases, possibly merging with another compatible strain (termed "plasmogamy") during mycelial growth, producing heterokaryotic mycelium, which itself can produce sclerotia and cycle through the mycelial growth/sclerotia forming cycle again.

If you are getting dizzy just reading about all these repeating cycles, it might be a good time to take a break, fire up your Internet, and check out www.wisc.edu/botany/fungi/morel.html. This is the website of Dr. Tom Volk at the Department of Biology and Microbiology, University of Wisconsin. There you will find an excellent pictorial representation of the morel lifecycle, and an explanation of the form and function of the sclerotium, plus a lot more important and useful information on morels and other myco-topics that could keep you busy for quite a while.

Ok, gentle reader, you can go ahead and surf the net for the rest of the day, or we can get busy making some spawn. A common recipe is based on the pioneering work of Ronald D. Ower, who was the first to produce morel fruit-bodies in a controlled fruiting chamber at San Francisco State University in 1982. His findings were originally published in Mycologia 74(1), Jan-Feb 1982.

Ower went on to develop specific techniques in conjunction with Gary L. Mills and James A. Malachowski, and in June of 1986, patent No. 4,594,809 was assigned to Neogen Corp, East Lansing, Mich., with the three named as the inventors.

The temperature, humidity, substrate and other detailed parameters were provided by George Robert Trager, according to the "Mushroompeople" website. The summary and a pictorial step-by-step guide can be found there at www.thefarm.org/mushroom/morel.html. Here is a somewhat similar description of spawn creation:

Making spawn

  • 5 parts annual rye grass seed (or other grain)
  • 1 part potting soil

Cover grain with water. Soak 24 hours. Drain. Mix with potting soil. Place 2cc of this into each 1 qt canning jar with micro-porous filter in the lid. Sterilize 1 hr @ 15 psi in a pressure-cooker.

Once cooled, the usual sterile transfer techniques can be used to insert a few small pieces of mycelium from your agar culture into the spawn jars. Reseal. Cover with foil. Shake and store in dark, cool (69-71 degrees F.) location. Four to six weeks later you should observe whitish mycelial threads throughout the medium. After five weeks, you should also see white to rust colored masses forming. These are the sclerotia.

Final Substrate and Fruiting

Once the mycelium has grown throughout and numerous sclerotia have formed, it is time to get creative. Depending upon where and under what conditions you will attempt to induce fruiting, several methods have been published, both for indoor culture and outdoor "garden" or "habitat" culture. The aforementioned patent gives a detailed account of two possible indoor fruiting techniques.

Paul Stamets has also published thoroughly researched and proven techniques for outdoor culture.

From my own observations, several conversations with respected individuals, and other research, including adaptation of some parameters taken from published material listed in the bibliography, I shall propose the following guidelines as recommended steps and components. You can base your own experiments on my suggestions as your adventuresome spirit directs you.

  1. Prepare the "supersoil" substrate, the standard mixture is as follows: 20 percent sand, 30 percent soil, 50 percent organic material composed of 80 percent small wood chips, 10 percent rice hulls, 5 percent soybean meal, 5 percent sphagnum. Correct the ph with lime to 7.1-7.3. Mix well. Saturate with H2O. Pasteurize in trays or fill sterile trays with pasteurized mixture. Trays should allow for slow drainage.
  2. Separate the sclerotia by hand from the grain spawn. Divide larger pieces if desired. Gather sclerotia from several different isolates. For each tray of substrate, inoculate with about 1,500-4,000 cc sclerotium per meter of substrate.
  3. Refrigerate for about one month at temperatures just above freezing (35-40 degrees F.).
  4. Remove from refrigeration. Allow the substrate to return to 65-70 degrees F.
  5. "Flood" with sterile H2O. Leave for 24 hours, then allow to drain slowly. Optionally apply casing to 1/2 inch thick (see Stamets recommendation for casing).
  6. Allow 7-10 days @ 65-70F for formation of primordia. Location should be dark with one to two air exchanges per hour.
  7. Once primordia have formed, you may break out a moderately priced bottle of champagne, or perhaps a nice "methode-champenoise" California selection. I recommend a lovely Schramsberg Blanc-de-Noirs. Before it goes to your head, though, you should: Adjust your substrate to 60 percent moisture, relative humidity to 85-95 percent, air temperature to 70-73 degrees F., and air exchanges to six to eight per hour. Light should be maintained on an on/off 12 hour cycle. Regular grow lights may be used. Alternatively, mild indirect or shaded natural light, possibly supplemented with artificial light during the short-day seasons, should work as well.
  8. In three to seven more days, adjust parameters for full fruit-body maturation: Substrate moisture 50 percent, relative humidity 85 percent, air temp 10-15 degrees C., and fresh air exchange at 6 to 8 per hour.

Once your mushrooms have reached a length of 126 mm, you may justifiably break out the Dom Perignon, and party on! This is the length of the fruit body first reported by Ower, and this qualifies you to enter a very small circle of individuals either very talented, very lucky, or both, that have successfully fruited morels under artificial conditions -- on purpose. Don't forget to take plenty of pictures before you cook them up.

Sources

Bibliography

Glossary

Terri Terri Marie Beauséjour (Bo' say zhur) is a past-president of the Mycological Society of San Francisco and was chair of the society's Cultivation Committee. When not on the road to mycological adventure and discovery she works as a senior software engineer for a leading computer-aided design firm. She can be reached by email (russula@home.com) or by regular mail c/o Mycological Society of San Francisco, PO Box 882163, San Francisco CA 94188-2163.