What Is a Mushroom Log and How to Care For One

A Bit About Your Log

We use fresh logs from a farm in Gloucestershire. Every year branches have to be trimmed back around the edge of the fields to allow tractors to pass, so all the logs we use come from trees that are still standing and healthy. Normally the branches would be dried out and sold as firewood but we think that turning them into food for gourmet mushrooms is more fruitful!

When they get to us they are assessed to make sure they are healthy and that no other competing organisms have settled in already. If in doubt we put them aside to be autoclaved, this ensures your mushrooms don’t have any rivals to contend with while colonising the log, which makes for happy healthy mycelium!

As you can see, there are a number of waxy spots on the log. To inoculate the logs we first soak 35mm long wooden dowels in water, sterilise and then mix them up with colonised rye grains. After some time, the mycelium from the grains identifies the dowels as a food source and weaves its way into the wood. Once the mycelium becomes established we drill some holes in the log and tap a colonised dowel into each one. It doesn’t take long for the mycelium to realise its surrounded by a new food source and start getting to work colonising your log! The holes then need to be sealed with wax to prevent the log from drying out.

How to Care For Your Log

Like us, mushrooms need water to survive so it is important to keep the log from drying out. The best way to ensure this doesn’t happen is to keep your log in a shady spot, outdoors and ideally shielded from the wind. Even so, the log will slowly dry out if conditions are warm and there hasn’t been any rain, so the log will need to be routinely watered. You can do this either with a hose or by dunking the log in a bucket of water for 10 minutes once or twice a week. When conditions are cooler or there has been frequent rain this won’t have to be done so often. If you notice cracks appearing in the ends of your log it means that it has been getting too dry and is in need of a more thorough soak. When this happens we recommend leaving your log submerged in water overnight and increasing the watering frequency.

Logs can be kept indoors or outdoors, if kept indoors special care needs to be taken to ensure it doesn’t dry out. It’s important to keep it away from any heat sources. If storing long term, like during the initial incubation when the mycelium is still colonising the log, keeping it in a semi-sealed environment like a cardboard box, or wrapped in a blanket can be a good idea as this will slow the drying process. It can be thought of like a loaf of bread you want to keep from going stale.

How to Initiate Fruiting

Mycelium typically takes 6-9 months to fully colonize the log. During this period, mycelium is content with the available food and does not produce mushrooms. To encourage fruiting:

• Method 1 – Cold Shock: Submerge your log in cold water for 24 hours. We recommend freezing water in tupperware or takeaway containers to create ice blocks, as larger blocks melt more slowly, keeping the water cooler for a longer time. Ensure the log is fully submerged, which may require securing it with string and a weight like a rock or brick before placing it in a bucket. Alternatively, you can place the log in the fridge for 24 hours. This method tricks the mycelium into thinking its environment is changing, prompting it to produce spores, which are necessary for mushroom growth.
• Method 2 – Give It a Knock: Another way to stimulate fruiting is to gently knock the log against a solid surface, such as a paving stone or concrete, or lightly tap it with a hammer. This simulates a colonised branch falling naturally from a tree, signalling to the mycelium that it's time to produce mushrooms and release spores

Harvesting

Once you see mushrooms they can be picked by gently pinching at the base of the mushroom and twisting off the log.