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  • How to grow oyster mushrooms in logs

    This instruction relates to growing Oyster Mushrooms from dowels; these are intended for inoculation into hardwood logs. Cultivating mushrooms from logs can be slow at 6-12 months, but gourmets comment that the taste of log-grown Oyster is much preferred over faster growing substrates. Oyster dowels can be used for inoculating tree stumps, sawdust, straw, paper products or a variety of alternative substrates, however these instructions cover the use of dowels in logs only.

    Mushroom dowels are wooden plugs around 40mm long and usually 8mm in diameter. They should be damp and will be covered in what looks like white or grey mould, often fluffy in appearance. This ‘mould’ is in fact the Oyster Mushroom mycelium. You will require sealing wax; once the dowels have been inserted into the log, you’ll need to seal the wound with non-toxic, natural sealing wax to prevent other fungi (including moulds) entering the log. This wax is available in 200g or 1000g bags; the smaller bag is suitable for around 100 dowels.

    Oyster Mushrooms

    You will also need a method of heating the wax in order to melt it and a small brush or foam pad for applying the wax; you will require a collared dowel drill bit and drill, hammer and the hardwood logs of 5 to 8 inches in diameter. Alder or Oak is the best choice, but most hardwoods will work fine. Don’t use cedar or softwoods because the resins contained within these woods acts as a natural fungicide, which will prevent the Oyster Mushrooms from growing.

    The dowels can also be used to produce mushrooms from the stumps of recently felled trees and will cause the stump to decay mush faster than it would have done otherwise, making its removal easier as well as providing you with a tasty dinner! Logs should not be used freshly felled; wait at least 3 weeks and up to 12 weeks before inoculating the logs. Older logs can be used but you run the risk that they will have already been contaminated with competitor moulds or other fungi. If you wish to use old logs, you can do so provided that they have no rot, although you would be well advised to heat the logs to 70 degrees C for 2 hours to kill off any potential competitors.

    Use your dowels as soon as possible – the sooner they are used, the more virulent the mycelium will be. If you cannot use the dowels straight away, you can store them in a fridge between 1 and 5 degrees C for up to one month. A pack of 50 dowels is sufficient to inoculate a log of approximately 1.5 to 2.5 m in length (diameter of 10 cm). If the log is split or has damage to the bark, we advise that you select an alternative, as the damage site is a potential entry point for competing species.

    Place the log which you intend to inoculate onto a saw-horse or bench. Insert the drill bit (10mm) into a cordless drill or similar and set the collar depth, such that a 50mm hole (depth) will be drilled. Drill the holes in a diamond pattern, covering the entire bark surface. With clean hands, insert a mushroom dowel into each hole and hammer it until it is flush with or preferably slightly below the surface of the log. Once all the dowels have been hammered home, melt the wax and apply a few drops of hot wax to the exposed dowel end, in order to sterilise and seal the surface, thus preventing potential competitors entering. If there are any side-branch wounds on the log, seal these too.

    Place the log in a cool, damp place for approximately 12 weeks. Do not cover with polythene, as this can encourage moulds to grow on the surface of the log. When the ends of the logs show signs of mycelial growth (you should see white patterns on the cut top and bottom surfaces), you know that the mycelium growth is complete. Leave the log to fruit naturally – Oyster logs will normally produce two crops per year – during the spring and autumn, and will usually continue to produce mushrooms for around 5 years. To encourage mushrooms to fruit, you can try sprinkling with water daily; with luck, within a few days, your mushrooms will erupt from the bark surface.

    Store the log in a location that you can keep watch for potential mushroom flushes – you don’t want to miss them! If you are not rewarded with a flush of mushrooms, don’t give up. Mushrooms by their nature are unpredictable and the log may simply need more time. Be careful not to allow your Oyster logs to get too wet or too dry. Ideally, store your logs in a shaded area (under trees) which will naturally provide the right conditions. Growing mushrooms outdoors can attract slugs, mites, flies, fly larvae and mice – pesticides should not be used as chemicals can easily be taken up by the mushrooms. Oyster Mushrooms need a little light, humid conditions and good ventilation. If your mushrooms have long stems with small caps and a deformed appearance, you need to improve the growing conditions.

    Thanks to Clifford Davy of Forest Foragers.

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