Originally published on April 18, 2016
Part of the secret to growing great oyster mushrooms on straw is pasteurizing the straw. In this excerpt from Mycelial Mayhem: Growing Mushrooms for Fun, Profit and Companion Planting, David and Kristin Sewak explain the basics of pasteurization and the steps for growing oyster mushroom on straw.
Straw is a great medium for growing oyster mushrooms, and when you first get into production growing, straw is the way to go. You get a fast run, so you can basically plan your harvest almost to within a few days. Following is a great method for making “quick” mushrooms and great mulch, and it can done indoors or outdoors.
Oyster Inoculation. Shroom Classroom participants pasteurizing straw.
We learned a lot about pasteurization of straw when we decided to sell and market our mushrooms. At first, we tried just soaking bales of straw and then inoculating. Dave read somewhere that all you had to do was fill up a tank (not heated), drop a bale in, put some concrete blocks on it, and let it soak for a couple of days. This method was not the greatest mushroom producer, but it did produce a strained back from trying to get a fully soaked bale of straw out of a tank! It has been known to work well in warmer climates, where the spawn runs faster. It also produced a myriad of other “mushrooms” and molds and ended up being a housing project for crickets, earwigs, slugs, and other critters we did not care to have around our mushrooms and garden.
Here is what we learned about pasteurization after a couple of years of trial and error: You need to pasteurize the straw in hot water. Pasteurizing straw for oyster mushroom cultivation requires you to soak your chopped straw in 160°F water for an hour. We use a turkey fryer burner as our heat source.
Dave unloading pasteurized straw.
Equipment and Materials Needed
- Oyster mushroom spawn appropriate for straw production.
- Polyethylene sleeves for production or spawn bags with filter patches (patches with a filtered opening to allow air circulation) for grow kits.
- A way to seal the bags — twine for large sizes or vacuum sealer for small ones.
- Straw bales — not hay.
- Pasteurization equipment: a 55-gallon metal drum from the food industry (not industrial) and a heat source, such as a propane-heated turkey fryer base.
- Waterproof thermometer to hang in barrel (a candy thermometer works great).
- Heat-proof mesh bags to hold the straw submerged in the barrel.
- Clean wheelbarrow, preferably with a small hole in the bottom, to drain excess water from the pasteurized straw.
- Chipper/shredder. It is best if you can chop up your straw. This gives you more substrate surface area, and allows greater compaction within the bags.
- A tool to make holes in the bags. A 2 × 4 with arrowheads in it works great
Shroom Classroom participants filling oyster bags with straw and spawn layers.
(complete instructions can be found on pages 51-54 of Mycelial Mayhem)
- Fill the barrel with water and heat to 160°F.
- Chop up your straw with a chipper/shredder.
- Collect the straw into large, mesh laundry bags, preferably ones with sturdy drawstring straps that you can attach to the chipper/shredder to collect the straw.
- Pasteurize straw in 160°F water for at least one hour.
- Carefully remove the straw from the barrel and empty it into a clean wheelbarrow with a small drainage hole in the bottom.
- Prepare the grow bags by placing straw and then oyster mushroom spawn in alternating layers, each time shaking the bag to more evenly distribute the spawn and compact it so you can get more in the bag.
- Seal each bag, larger ones with bailing twine, smaller ones (such as the grow kits to sell) with a vacuum sealer.
- Poke holes in each of the large production bags (but not the smaller ones with filter patches).
- Hang the larger production bags in the shade near access to a watering system.