Falling for an Autumn Log Inoculation 
at Field and Forest Products
Written by Joe

A change in leaves means it's almost time for fall inoculation here at FFP.

Autumn has definitely arrived here in the Northwoods. Our first killing frost was the week of September 12th. The geese are starting their journey south, and the bracken fern on the forest floor has browned and is beginning to topple over. This all adds up to dreams of late season brook trout fishing in the morning, coupled with a ruffed grouse hunt in the afternoon, but alas reality dictates otherwise.

I guess we have no one else to blame other than ourselves for our new found log inoculation schedule. In February of 2010 Mary Ellen and I took a tour of log grown shiitake operations in Japan and noted that the large operations (100,000 plus logs) did all of their inoculations in the fall of the year, and either held the logs inside for incubation or outdoors in plastic wrapped piles. Unlike growers in our southern states who preferentially inoculate in the fall and through the winter, we tend to lay low in the late fall and toss back cheese curds to bulk up for the onslaught of winter weather. However, last November when the kids were home for Thanksgiving break they begrudgingly agreed to help with a fall inoculation trial. We had several large oaks and oak branches become available as a result of stormy weather in September, and having the firewood larder filled, we thought it would be a good test to fall inoculate this wood and incubate it inside over the winter. In one day we knocked off about 60 logs using thimble spawn. The logs were crib stacked, covered with cardboard and then sealed in black plastic. The logs were held in our fruiting room where the temperature is generally 65-68°F with a relative humidity of 90-95%. The logs were placed outside in late May when winter finally ended (or so it seemed!)

This wide range strain, WR46, was inoculated Thanksgiving 2010.

The results this past growing season were favorable. We had volunteer fruiting at seven months of age, and logs were forced fruited at nine months with good results. It dawned on us, as we were finishing our 2011 inoculation in late June(!) that due to the nature of our business, it would make much better sense to fall inoculate logs when time and staff were readily available.

This past spring we met a local landowner who is in the process of thinning a hard Maple stand and expressed an interest in selling us shiitake logs as most of the wood being cut is between 3-6 inches in diameter. After a moment’s thought, of course we said “Yes, and please cut 500 of them for us.” It dawned on us later that perhaps there isn’t enough room inside for incubating 500 logs in our limited area, but with the help of a tape measure and some assumptions on log diameters it was calculated that we have enough room for just under 1200 logs in our allotted space. We assumed approximately 18 logs per lineal foot at breast height.

The logs are being cut in the next week or two and we will start inoculating by late October. We are hoping for an extended autumn with mild temperatures and rain falling other than during work hours, as we plan to inoculate outdoors as much as possible. The bet is on, that the weather will not cooperate, and there will be a million and one other things to do. We will probably end up inoculating indoors, but that is alright too.

This Japanese grower is showing us the spawn run on the ends of his indoor incubating logs.

We will be using thimble or waxless spawn for the inoculum because if we do have to move the inoculation process inside, we will not have to deal with wax smoke filling the workspace. We also like waxless spawn for this application because other than eliminating the waxing step, spawn rebound is excellent when logs are held in a warm humid environment. Wide range strains will be used for the most part as we would like to get some production from these logs for late summer farm markets next year. We will also be using WW44, a warm weather/greenhouse strain, as it has been shown to do well in Sugar Maple.

The inoculation flow will be set up in such a way that the logs will move from the stacked piles outdoors to the inoculation bench and then into a dead pile (logs simply stacked horizontally atop one another, ends all in the same direction), all placed on top of palettes set in long rows. The exception to this is the pallets at the row's ends where the logs are stacked in a crib (log cabin style) to shore up the rows. Once all logs are inoculated the dead pile will be covered with cardboard on the top of the pile to act as a sponge to collect moisture, and then the whole shebang will be covered with black plastic. The plastic will be stapled to the palettes and then the waiting begins. We did not water the logs last year during incubation and probably will not do so this year.

It is always hard to ignore logs in piles, particularly when they are in your way. So from time to time we will take a peek inside the plastic to see what’s happening. Visible spawn run on the ends of the logs is always a good indication that things are progressing.

For growers in the upper Midwest and northeastern U.S., fall inoculations are less encouraged because the window of time (cutting at first blush of leaf color and achieving inoculation at least 3 weeks prior to daytime highs settling into the low 40’s) is almost impossible to achieve. However, a variation on this fall inoculation theme could help make a fall inoculation with OUTDOOR incubation more feasible. Once the logs are inoculated, they are dead piled and covered as above, but outside where they will receive daytime solar heating. This will provide some additional growing time for the spawn to get established in the log. The plastic/cardboard will have to be removed and the piles broken apart and placed in their permanent outdoor yard in the spring of the year when daytime temperatures start to reach the 70°F mark.

These logs are incubating through the year with a winter inoculation in Japan. Notice the crib stacked logs on the end to stabilize the piles and the covering of cardboard, then plastic, then rice mats to provide shade during the summer months. Take note that the temperatures in Japan's main shiitake growing region rarely get above 80°F and cloud cover is generally the norm.

Meanwhile, maybe mushroom growing Packer fans can rest easy and don their cheese hats come January, knowing that most of the work is done for spring. Me, maybe I’ll get out opening day of trout season for the first time in a decade (or more) instead of schlepping in logs!