Thursday, 17 February 2011

Mushroom growing

I went to a free workshop at Cannor Nursery a couple of weekends back, to learn about mushroom cultivation. The speaker, Gary Hagel,

has been growing mushrooms for about three years and offered to share some techniques and ideas about it. It was a very full morning.

His interest is not restricted to growing mushrooms for food; he's also interested in the capacity of mushrooms to break down hydrocarbons. He recommended his personal "mushroom bible" by Paul Stamets: Growing Gourmet and Medicinal Mushrooms. Stamets elaborates on the environmental and disease-fighting aspects of mushrooms on his TED Talk: Six ways mushrooms can save the world.

We started off with a demonstration of cloning mushrooms, which he says is the easiest way to propagate. He illustrated some of the sterilization techniques involved - without them you can end up with molds and bacteria that will kill off your mushrooms and leave you with a big green mess. To get underway, following the Stamets methods, you'll need an assortment of items, including:
  • A good book (as stated)
  • A glove box (you can make armholes by heating a coffee can and burning through the sides)
  • Rubbing alcohol
  • Hydrogen peroxide (don't know what strength - I'm guessing stronger than you'd get over the counter at a pharmacy)
  • A pressure cooker with pressure valve
  • Jars, suitable for pressure cooking, with screw-on lids
  • Hypodermic syringes
  • Scalpel
  • Lighter (for sterilizing needles)
  • Micro pore tape
  • Tinfoil
  • Large clear plastic bags
  • Agar (can buy in Chinatown)
  • Heavy duty plastic bags with ventilation patches (specialist item)
  • Growing medium (organic and/or untreated rye, corn, chickpeas etc)
  • Depending on what kind of mushrooms you want to cultivate, you'll also need straw (buy at garden supply stores) or hardwood chips/sawdust (buy from pet supply stores: do not use coniferous wood, and especially not cedar which has bactericidal properties) or hardwood logs with intact bark (alder is popular on the island; oak or maple can also be used)
He started with instructions on cloning mushrooms, which he says is the easiest method of propagating; you can do it with any mushroom you buy.

You'll need a prepared (sterile) growth medium; he used rye grain, because it was cheap and available from garden supply stores, but says corn and chickpeas work well too. Wash it and then soak it in water and gypsum for 24 hours. Drain and spread on cardboard to dry for around 2 hours. put in a sterile mason jar. Cover barely hand-tight with a screw-top lid that has had its top punctured and then sealed with micro-pore tape. This will prevent micro-organisms from finding their way into the sterile medium. (The one shown contains a month's worth of mycelium already)

Cover the lid with tinfoil. Place on a rack (or on a base of screw-top lids) in a pressure cooker and add water. Pressure cook for 90 minutes at 15 lbs pressure. Then move on to the cloning.

First you sterilize your glove box by wiping it with alcohol. This removes bacteria and microorganisms that would interfere with the growth of the mycelium.

Then using a sterile scalpel (and presumably wearing sterile gloves) nick a piece of mushroom off.

Dip it in hydrogen peroxide and place into the sterile growing medium. Put it somewhere dark and warm (75f) for about one month.

Prepare some straw or wood chips or make plugs to grow it in logs. To prepare straw, steam it for about an hour to get rid of any mold or bacteria. Dry it and put it in clean, sterile (wiped out with alcohol) bags. Pour in the aged, inoculated rye grains and give it a shake. Cut slits in the sides of the bags so the mushrooms can fruit. Return to warm, dark environment and mist the outside of the bag daily. When the mycelium has developed through the straw, it's ready to fruit and for this needs oxygen and light.

Oyster mushrooms, above, which grow best in straw: just twist gently to harvest. Once fruiting has completed, soak the bag in a tub of water for 24 hours and will fruit again, another 3-4 times. It only takes about a week for oyster mushrooms to fruit.

Propagating with spores is more time consuming, and involves agar and petri dishes. Spores are easy to collect: place a mushroom on tinfoil for 24 hours and you'll have them. But you'll have to do this in a sterile environment, and scrape the spores into sterile water and transfer them in a sterile needle onto sterile agar in a sterile petri dish. But it's a useful technique for specialist mushrooms - such as mail order ones - where you may only have spores to work with.

Other mushroom varieties were discussed briefly: button mushrooms (grown on compost) and chanterelles (best to collect wild as the mycelium is extremely slow to grow, taking years in fact).

He led us through liquid culture, which involves honey and water, and is useful for cultivating shiitake mycelium for long-term storage (keeps 6 months to a year in the fridge). Dissolve 2 tbsp honey in a jar 3/4 full of tapwater. Prepare the jar lid by puncturing it and sealing with epoxy.

Close, barely hand tight, cover with tinfoil, and pressure cook in water on a rack for one hour at 15psi. This is the sterile growing medium. Add mycelium to the water using a sterile needle, and keep warm and dark for about 1 week after which it can be used or stored in the fridge until needed.

Remove mycelium with sterile needle and use to inoculate wood plugs (for growing in logs) or wood chips.

To grow in wood chips (available from pet stores) use poplar or any hardwood. Mix 80 per cent wood chips with 20 per cent bran in a big bowl.

Soak, strain until moist but not wet. Place in a special heat-resistant bag (sterile, plastic, with a built in screen for filtration). Add a piece of clean tyvek to the neck of the bag and pressure cook 2 hours at 15 psi.

Add the mycelium in the sterile glove box. Seal and keep at 70f in the dark for about 3 months.

When mycelium threads start showing, soak the bags for 3 days and then open to let the mushrooms fruit.

To cultivate in logs takes about 2 years, but after that they'll go on producing for about 9 years. Alder, oak, maple are good choices. Not cedar or conifers.

Prepare the spiral groove dowel plugs

by half-filling a jar and then pressure cooking them at 15 psi for half and hour. Add the mycelium and keep warm and dark for about 2 weeks.

Scrape lichen and fungus off the logs, but not the bark which is an essential part of the process. Drill holes

and place inoculated spiral groove dowelling plugs in them. Seal with wax or Seal n Heal.

Put about 20 plugs in a 4 foot log. They'll need moisture - soaking with a garden hose - and protection from wind.


  1. thanks Rhona

    I missed much of Gary's presentation at the GTUF meeting so it is great to have this opportunity to catch up. I have a mushroom log - alder plugged with ready-made shitake plugs. I'm hoping for a crop this fall!

    of SJUF and Reskilling WG

  2. Well now I have got here, at last I don't want to leave - what a great blog.
    I'm going to share it with the urban farmers in my neck of the woods