Trench Log and Log Raft Cultivation

Grow mushrooms on logs for the simplest way to cultivate edible and medicinal forest mushrooms.

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Tradd and Olga Cotter
Using the raft or trenched log method, you can produce an overwhelming number of fruitbodies in a single flush. All the mushrooms on this colonized raft are considered one organism, because the mycelium fuses and connects.

People have been growing mushrooms on logs for hundreds of years. It’s one of the simplest ways to cultivate edible and medicinal forest mushrooms.

Many mushroom species that thrive on wood fruit better on logs that are partially buried rather than stacked aboveground. The access to extra ground moisture, reduced fruiting surface area, and microclimate created by covering the logs with leaves or straw trigger and support prolific fruitings preferred by (but not limited to) reishi (Ganoderma spp.), nameko (Pholiota nameko), black poplar/pioppino (Agrocybe aegerita), brick top (Hypholoma sublateritium), and maitake (Grifola frondosa). There are basically two ways to do this: either you trench the logs, or you build a “raft” of them and cover it; they both produce the same results.

When you cultivate mushrooms on partially buried wood, the flushes typically only last for two to three years, so be prepared to build additional beds every two years to sustain a continuous harvest. That said, certain mushrooms can fruit heavily in that timespan. I’ll describe two methods; your choice will depend on your access to fresh wood chips. Whichever method you choose, first drill holes in your logs, insert plug or sawdust spawn into the holes, and allow them to colonize for three to four months aboveground. Water these logs weekly for the first two months. Once the beds are prepared, you only need to water the logs and saturate the beds around the time the mushrooms should fruit.

Trenching your logs means you’ll need to excavate a space half the depth of your logs, long and wide enough to fit all the logs in tightly. After you place your logs in the trench, shovel the soil you removed back in between the seams and gaps and around the edges. Then water the logs so the soil settles in firmly, leaving the clean upper bark surface exposed. (You could bury them entirely, but finding them again can be difficult, and you don’t want to step on any mushrooms that may be hidden and working their way up through the leaves and mulch.) Place a stake or sign near your bed so you can mark where you have planted, and label it with the date and strain information for your records.

Log raft cultivation is similar to trenched log cultivation, only it takes place aboveground. Lay down a thin layer of wood chips, mulch, sawdust, or soil, and then wiggle the logs into place so they lie tightly together in a row. Fill in the seams and gaps, build up a layer of substrate all around the edges of the bed, and then water heavily. Wood chips are especially helpful for log raft cultivation; they give the bed an extra food source and help retain water for the developing mushrooms when they fruit.

Once the logs have been trenched or set up in rafts, water them once a month. When you begin to see fruit, mist them daily.

Excerpted from Tradd Cotter’s book Organic Mushroom Farming and Mycoremediation: Simple to Advanced and Experimental Techniques for Indoor and Outdoor Cultivation (Chelsea Green Publishing, August 2014) and is reprinted with permission from the publisher. Tradd Cotter is a microbiologist, professional mycologist, and organic gardener, who has been tissue culturing, collecting native fungi in the Southeast, and cultivating both commercially and experimentally for more than 22 years.

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