Is it Too Late to Inoculate? A Lesson in Log Sitting.

Information on how long you need to wait after wood is cut for mushroom cultivation is all over the map. This is with good reason, we live in a big country with lots of climate zones and lots of different wood types, all which can affect the aging process.

Mushroom mycelium needs 2 things to get a good start into colonizing a piece of wood. It needs air, and water, and eventually wood which is the ultimate food source. To start though, the wood you have carefully selected from a living green tree is filled with water. The free water that is loosely bound in the wood needs to start to evaporate, or dry, leaving air space and room in which the mycelium can grow. Depending on where you live and when you cut can give you a big range of time from cutting to inoculation, say, from 2-4 weeks to even 6 months in very northern areas. Those of us who live in locations where our logs are covered with snow after cutting have a long wait for the wood thaw and to start drying. Those of us in the warm South have less time, maybe 2 months if the logs were winter cut.

The drying process starts immediately after cutting. But HOW LONG it takes to start emptying the wood cells of water depends on 3 main factors:

1.Temperature and humidity of the air around the log after cutting: warmer climates will dry wood faster than cold climates.

2.Bark thickness.... Thick barked wood pieces take longer to dry than thin bark

3. Wood species have variable drying rates, white oak takes longer to dry than say, red maple

Log Varieties

These January cut logs, with proper storage, still look fresh in April.

So where you live and when you cut your wood makes a big difference in how long you can safely wait until you inoculate.

How do you know if you waited too long to get your wood inoculated and the wood dried out too much? Fortunately, the wood itself can give us good clues. Feeling the heft of the wood, examining the color of the inner bark and dampness on the log ends give an experienced grower most of the clues they need to judge the condition of the log. For those of us newer growers, checking the appearance of the ends of your logs is the easiest way.

Wood dries from the outside in, but because the moisture is being pulled outward from the wetter center, the logs will start to crack from the inside out, from the pithy center to the bark. Look for hairline cracks from the center moving outward. Ideally, cracks should extend no more than 1/3rd to 2/3rds from the log's center. This can take weeks to up to months depending on where you live, when you cut the wood, how you store the wood, etc .

Another indicator is looking at the width of the cracks.

Cracked Ends

The same January cut logs, stored indoors in a dry environment, may need soaking prior to inoculation.

If you can stick a dime in the biggest cracks, the wood is approaching the "too dry" phase, termed "fiber saturation point " where the free water in the wood cell is gone and now the bound water within the wood cell wall is drying up, physically changing the structure of the wood and it's ability to support good fungal growth. This occurs when the wood is approximately 20-30 percent moisture. You can take a moisture test by cutting a wafer of the wood, drying it and calculating the moisture content, or just looking and feeling the surface of the log end. It will feel very dry.

Log wafer in oven

You can get a moisture content reading of your logs by doing a wafer test.

* To calculate the log moisture content: Take the wet weight of the log section minus its dry weight and multiply it by 100, then divide that figure by the wet weight of the log section and that will give you the log's moisture content.

What happens when inoculation is delayed and the logs have these deep cracks?

You can soak the wood for 24 hours to re-establish some moisture. Let the logs dry for at least another day after soaking to let the wood cells drain of excess free water that has accumulated in some of the now permanently altered cells. Because the mushroom mycelium tends to have sluggish growth in these too-dry logs, these logs that have been inoculated after soaking should be carefully monitored during future dry spells during the growing season to give them all the TLC they need to support abundant harvests in the future!

Soaking Logs

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