In this blog, we will be discussing when and how to harvest logs for shiitake and oyster mushroom plug spawn. We will discuss the inoculation process in the next blog series.
Overview of Tree Dormancy
Every year during the fall, the leaf canopy begins to change color and the leaves eventually fall to the ground. This is nature's sign to let us know that the season is changing and that the tree is beginning to go into winter dormancy. During winter dormancy, the nutrients that once supplies the fruit and leaves to the outer branches of the tree begin to migrate back to the center of the trunk and back down to the root system. Many people refer to nutrient migration as sap flow. In the winter, the sap falls and in the spring the sap is rising back out to supply the outer branches of the tree.
Log Nutritional Content & Seasons
If you plan on harvesting a tree for plug spawn, the best time to harvest the logs is when the tree is dormant between late fall and early spring. This is when the cambium and sapwood of the tree have the most available nutrients for the mushroom mycelium to thrive. Once the sap has begun to rise, there will be less available nutrients. If you do decide to inoculate non-dormant wood, do not expect as large of a mushroom harvest. The logs also tend to not last as long as dormant wood because the outer bark will fall off faster exposing the mycelium and inner wood to other microbial competitors. This does not mean that you cannot harvest trees year-round though. Many people harvest trees throughout the year and use trees that have fallen during the spring and summer months for mushroom cultivation. See below for the best times to harvest your logs for mushroom cultivation.
You can determine if the tree is still dormant by looking at the buds on the branches. Below on the left you can see that the buds are still tight and have not started to swell. On the right, you can see that the buds on this branch have started to open and this tree is no longer dormant.
Tree Selection
You will need to select a hardwood species that is suitable for the mushroom strain you wish to grow. I primarily focus on Shiitake and Oyster plug spawn because they are the easiest and most rewarding strains to grow. The tree you select should be at least 4-6" diameter at the base. If you choose a much larger tree, keep in mind that the logs will be much heavier and harder to handle. Shiitake mushrooms do best when grown on a harder wood such as oak while oyster strains can be grown on softer hardwood varieties. See the below table for several recommended species. This list is not all inclusive. Be sure to check online to verify if the species you select is suitable for mushroom cultivation of your choice.
Tree Identification
Identifying trees during the winter months without leaves can be difficult. If possible, it is a good idea to identify the trees during non-dormancy and mark the trees with spray paint so that you know the logs you want to harvest at a future date. If you are having a hard time identifying a species of tree, you can try a plant identification app. You can also Google images of the specific tree bark for assistant. Sweetgum is the easiest for me to identify and it works well with both Shiitake and Oyster varieties. In the image below, you can see that the smaller branches have what I call an alligator texture and are very easy to spot. Sweetgum is also considered a cull tree and is not suitable for millwork applications making it a perfect and easy choice to identify.
Log Size
For logs that are 4-6" diameter, cut them to length from 36 - 40", whichever size is easier for you to manage. Logs larger than 6" in diameter should be cut to shorter lengths so that you can move them around easier when inoculating and transporting the logs.
Log Storage Prior To Inoculation
Once you harvest your logs, you will need to let them season for a period of time between two weeks and up to three months if located in southern regions. The northern regions can season logs up to six months. When you season the logs, it allows the excess moisture to evaporate making it more suitable for the mushroom mycelium to thrive. However, a log can be seasoned too long. If this happens, you will need to rehydrate the log soaking it in water for 24-48 hours prior to inoculation. After you harvest your logs, it is best to store them in a stack elevated off of the ground. I use wood pallets and cover the stacked wood with a tarp until I am ready to inoculate with plug spawn.
Next we will be discussing the inoculation of the logs with plug spawn. Link to next in series:
Check out the Log Harvesting how to video below:
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