As I gain more experience and become aware of new information, I continually find that I need to make small changes to the peroxide manual to keep it in line with my current understanding of the effective use of the method. If I find significant pitfalls in a previously published procedure, I will let you know about it here. I will also post some news of advances in the procedures. Of course, new editions of the manual will generally contain additional material that has not been posted here.
This page is also evolving into a place for me to post announcements, such as new product offerings or new developments with the web site. So please check back regularly.
Go to Updates to the Third Edition
Go to most recently posted updates
2) My success rate for clean grain spawn (soft winter wheat) is now running close to 99%. However, after a relatively trouble-free period with bulk substrate, I had a rise in contamination of pellet fuel cultures of P. eryngii and H. erinaceus which I reported on my web page. This problem has now subsided. This may have been the result of a leak in my pressure cooker, giving me poor sterilization of my nitrogen supplements, but I also took steps to insure complete mixing of peroxide into the substrate, and to avoid having bits of pellet fuel falling out as I filled bags, then bouncing off a nearby surface and falling back into the bag.
In addition, I recently discovered that particulates were coming in with my tap water, which increased with the onset of the rainy season. Of course, all water used without pressure sterilization needs to be clear and free of particulates, which can carry peroxide-decomposing enzymes.
Finally, I discovered that small bits off sawdust were lodging on the outside of my 5-gallon bucket near the rim when I opened or closed the lid. These bits could then pick up contamination, after which they could fall into my final substrate bags as I poured the sawdust from the bucket. Now I try to watch for these bits of sawdust and brush them off before I fill each bag with substrate.
I now seal all my bulk substrate bags by tying off with twist ties. It turns out that H. ulmarius, H. erinaceus, and P. eryngii can all reach primordia formation in bags that have been sealed in this way, with no microporous filter. However, although I thought at first that this success was due to oxygen supplied by peroxide decomposition in the substrate as the mycelium grows, it now turns out that there must also be oxygen diffusing through the plastic bags themselves (since the mycelium will not grow in tightly sealed plastic buckets). So--If you use plastic trash bags to hold bulk substrate, as suggested in the manual, try to get the thin (0.5 mil or less) bags made of high-density plastic rather than the more common bags made of soft, thick plastic. The thin bags will allow better oxygen diffusion. And the thicker bags are most likely PVC, which may release endocrine-disrupting chemicals into the mushroom substrate. Also, I have been told that some of the thicker bags are impregnated with fungicide.
I have also recently concluded that the procedure for "cleaning" mycelium of occult contaminants is more important than I previously thought, and to assure successful cultures it should be performed regularly (at least every third transfer, or every transfer if you leave your agar cultures for a long time between transfers). This is true whether or not you are using peroxide in your final bulk substrate, but it is especially important if you are not. Be sure not to cut all the way through the agar when you remove agar wedges for inoculation from a bottom-inoculated plate. Also, it is a good idea to wipe counter tops and fingers with rubbing alcohol before performing the procedure.
3) It was brought to my attention that, when I talk about hydrogen peroxide as being safe and environmentally benign, I should say that I am specifically referring to peroxide at a concentration of 3% or less. Higher concentrations, such as 30%, 35%, and 50% are available, but these are quite hazardous.
It turns out the procedure for 10 Minute Spawn works best with pellet fuel made of light woods. Both fir and cottonwood pellet fuel have given me consistent success. When I tried oak pellet fuel, however, the pellets took a long time to disintegrate into sawdust on makeup, and I began getting many contaminated jars, presumably because the greater density of the oak sawdust slowed the heating and cooling process. It may be possible to compensate for these problems by increasing the amount of peroxide used.
I have at last succeeded in fruiting Agaricus subrufescens, the almond mushroom, on pellet fuel substrate (especially fir, but also cottonwood, and to some extent oak) prepared by the peroxide method. This mushroom seems to like a firmly packed sawdust substrate. I grow 6-7 lb blocks of mycelium, then combine 3 or 4 of the blocks into a larger culture (in a trash bag placed inside an apple box, for instance). The larger culture gets a 2 inch casing of 50:50 soil:peat with a handful of gypsum and enough vermiculite added to give a friable texture. Then I place the whole thing in warm spot, sprinkling the casing regularly, until the mycelium begins to show at the surface of the casing. Finally, I remove the box to a cooler spot, with plenty of air and some light, to allow the mushrooms to form. The yield so far has been small, just two pounds of mushrooms from an apple box of colonized substrate, supplemented to about 0.4% nitrogen. (Note added later: Yield seems to be improved by leaving the culture in a warm spot through the fruiting process).
A caution with processed supplements to be used without autoclaving: be careful that these supplements don't spoil in storage (or haven't already spoiled slightly when you get them). If they do, they will start to cause your peroxide to decompose, even if you pasteurize them. Keep them stored in a cool or cold place, and check them periodically by dropping some into a small amount of straight 3% peroxide solution. If they fizz, you won't be able to use them anymore without autoclaving them first.
Although I've used oyster shell lime for a long time, I recently found that this additive--after prolonged storage--can cause a low level of peroxide decomposition. Therefore, I now recommend ground limestone. If you can't find ground limestone, you can use hydrated lime (Mason's lime or builder's lime), but about half as much as you would use of limestone. I currently use 1 oz hydrated lime for 8.5 lbs of oak pellet fuel to make substrate for Hericium or elm oyster. Please handle hydrated lime with caution: it can burn skin, eyes, and mucous membranes. Do not use Dolomite lime, as it contains magnesium, which can inhibit mushroom development.
December 24, 1999: I've recently found that an overnight soak in vinegar can inactivate the peroxide decomposing enzymes in a sample of mycelium. Presumably other weak acids will have a similar effect. This may eventually prove useful in inactivating the enzymes that break down peroxide in raw drainable substrates like woodchips, cottonseed hulls, straw, or other agricultural wastes (as well as supplements like millet), so that they can be prepared with peroxide without prior pressure sterilization.
December 29, 1999: Experimenting with a sample of commercial birdseed, I find that an overnight soak in vinegar does not eliminate the peroxide-decomposing enzymes in the seeds. But 15 minutes of boiling the seeds in ten-fold diluted vinegar eliminates nearly all the activity of the enzymes. Apparently the boiling allows the vinegar to penetrate the tough seed capsules.
January 12, 2000: Happy New Mycelium!
On storing and drying agar plates: I've recently learned that the biggest factor causing decline in peroxide concentration in unused agar plates is probably evaporation of the peroxide. So if you dry your plates for a long time after pouring, or if you store the plates for a long time, you may get more contamination than you expect. This problem can be avoided by increasing your initial peroxide concentration slightly (if you expect to dry or store the plates for a long time), or by drying the plates for shorter periods. When storing plates, be sure they are sealed in an air-tight container or plastic bag.
On oyster shell lime: I've recommended against using oyster shell lime because it can "spoil" and develop peroxide-decomposing enzymes that will cause contamination in cultures. Now I find that fresh oyster shell lime has even more peroxide-decomposing enzymes than oyster shell lime I've stored for a long time. But there is a remedy: if you bake the lime in the oven (with plenty of ventilation!) at 400 degrees F for an hour, you can destroy the enzymes. Then you can freely use your baked oyster shell lime with any of your peroxide procedures.
February 3, 2000: Here are some pictures of what I do with my pellet fuel substrate. Nothing remarkable here, but I'm starting to generate a few "visuals" to go with the otherwise pictureless manual.
Inoculating a bucket of substrate
Filling a bag with inoculated substrate
The substrate sealed in a bag, inside a box
Jars of Ten Minute Spawn on a bookshelf
Some mushrooms growing equipment
Pouring agar plates
February 8, 2000: To help with locating some of the supplies called for in the peroxide manual, I have set up a "Sources" page. Unfortunately, this page right now will mostly be of help to residents of the US, although any information contributed from other countries will be gratefully added. Visit the Sources page
March 9, 2000: I've added some more contact information for Springfield Scientific supply on the Sources page, and corrected the phone number listed there for Pennington Seed.
A note on testing materials to see whether they are peroxide-compatible or whether instead they contain peroxide-decomposing enzymes: for the most sensitive test, add a little detergent to the peroxide. Then any bubbles that develop will appear as foam. Also, the detergent will help to wet the material, allowing the enzyme reaction to develop sooner if it is going to develop at all.
March 22, 2000: For those of you who want to inoculate peroxide-treated bulk substrate with commercially-produced (non-peroxide) spawn, doing this does not create a problem: the latest information I have is that the non-peroxide spawn grows easily into the peroxide-treated substrate without any appreciable lag to adapt to the peroxide.
April 5, 2000: There is apparently an ambiguity in the manual regarding the amount of water I use for preparing pellet fuel substrate. To clarify, I use roughly 7 quarts (or 7 liters) of water total for about 8 pounds (3.6 kgs) of oak pellet fuel, the water divided in half for the two stages of substrate preparation.
June 5, 2000: I've found that the distilled water storage method described in the manual is not as effective for long term storage as I had once thought. I have not been able to revive mycelium of P. eryngii, H. ulmarius, or A. subrufescens that I've stored for two years in distilled water. Therefore, I have to recommend that this method only be used to store mycelium for six months for most species (I was able to revive Hericium erinaceus after about 2.5 years of storage). Unfortunately, there seems to be no perfect storage method--even liquid nitrogen does not work in every instance.
June 20, 2000: I've added a couple of substrate ideas to the Sources page for people who live in the UK or nearby.
July 24, 2000: Kiln-dried sawdust (that is, sawdust produced by the milling of kiln-dried lumber) can now be added to the list of likely peroxide-compatible substrates. A sample of this kind of sawdust that I tested for peroxide-decomposing enzymes showed only very slight activity.
August 10, 2000: Just released! Volume II of Growing Mushrooms the Easy Way. Click on the title to find out what it contains.
September 6, 2000: After a break to solve some technical problems, I am again offering small (9 oz.) samples of spawn of Elm Oyster and Lions Mane to US and Canadian customers. (Almond mushrooms are still on hold.) For more information, click here.
September 30, 2000: A tip on cloning mushrooms: use the youngest mushrooms you can get, for rapid mycelium formation.
When preparing mushroom substrate for the peroxide method, be cautious about adding fertilizers or nitrogen supplements that contain added trace metals, especially iron, manganese, and copper. These metals will speed up the decomposition of added peroxide.
November 17, 2000: The new 3rd Edition of Paul Stamets's text, Growing Gourmet and Medicinal Mushrooms has been released! It can now be ordered through my link to Amazon.com (click on the title). This new edition has been expanded by over 150 pages compared to the 2nd edition, with new chapters on Agaricus blazei (Royal Sun Agaricus), Agaricus brunnescens (Portobellos), Sparassis crispa (cauliflower mushroom), and more.
R. Wayne