Here's the right way to start oyster mushrooms from scratch:

• Make a "clean room" into which spores of other mushrooms can't invade.
  
• Mix up some agar and make sterile petri dishes.
• Add a tiny section of oyster mushroom to each dish.
• Once the spawn runs across the petri dish, make sure nothing else is growing on the dish.  If you haven't created a clean culture, throw it away and start again.
  
• Fill clean canning jars about halfway with roughly equal quantities of grain and water.  (0.45 pounds of wheat or rye and 0.9 cups of water is about right.)
  
• Put sterilized filters on top of each jar so that air can come and go but fungi spores can't.
  
• Let the grain soak overnight, then cook the jars at 15 PSI in a pressure canner for an hour.
• Move the pressure canner to the clean room before opening.
• Let the grain cool.
  
• Cut the petri dish (with spawn) into sections and add some to each jar.  You can get away with adding 3% spawn by weight, but if you've got it, 10% to 20% is much better.
  
• Shake the jars to mix the spawn into the cooked grain.
• Incubate at 75 degrees Fahrenheit for two or three weeks until the oyster mushroom spawn has fully colonize the grain.

Maybe it's just me, but that procedure sounds pretty intense and far beyond the average backyard mushroom-grower's reach --- and I didn't even mention the part where you use the grain spawn to inoculate the fruiting medium!  Extreme measures are needed to keep one strain of mushroom pure for a big mushroom company, but what if you just want to expand your existing mushroom log collection slightly?

Last year, I experimented with growing oyster mushroom spawn on cardboard.  The jury's still out on whether that worked --- the trouble with mushroom experiments is that you often have to wait years before you find out if you were successful.  So I decided to experiment with a medium-tech way of growing oyster mushroom spawn in case the low-tech cardboard method doesn't pan out.

The vigor of oyster mushrooms (and the fact that I'm not planning on expanding my spawn more than once) allows me to ignore some of the sterility precautions.  Rather than jumping through all of the hoops outlined above, I simply soaked some leftover wheat overnight in open quart jars.  Next, I cooked the jars in the pressure canner at 15 PSI for an hour.  Once the grain had cooled, I spooned some into a couple of ziploc bags, leaving the jars halfway full.  Then I mixed in a bunch of oyster mushroom stem butts I'd collected off our bountifully fruiting mushroom totems this week.  I left the tops of the bags and jars open, but draped a damp cloth over them in hopes of keeping the contents moist.

I'm sure plenty of "weed fungi" got into the grain in my completely unsterile work area, but I suspect the oysters will outcompete those weeds pretty quickly.  As long as the spawn that appears is white, doesn't look greasy, and smells right, I'll assume my technique worked.  Then I'll be faced with an even bigger dilemma --- what to do with two gallons of oyster mushroom spawn when it's too late in the year for outside inoculation!