Following the spawn run your inoculated logs will be ready to “fruit”. Fruiting will likely begin the spring after inoculation. With proper handling and good management the logs should give you 4 to 5 years of production depending on the hardness of the wood, the diameter of the logs, and the integrity of the bark. The logs will produce mushrooms outdoors from May to November and can be fruited in a greenhouse during the winter months.
Shiitake is a saprophytic mushroom that survives by deriving food from wood lignin which it breaks down with enzymes and then absorbs. The mushroom organism (mycelium) that was introduced into the log last year has been busy establishing itself (the spawn run) in the sapwood under the bark of the log, and will eventually digest the heartwood as well. After the mycelium has established itself and has gathered enough nutrients, it will try to reproduce itself, given the proper environmental stimuli of temperature, humidity, and light. The mushrooms that the mycelium will produce are its means of reproduction – the fruiting bodies of the organism like the apples on a tree. If not harvested they will produce spores which will be released to the wind. The mushrooms must be harvested before they sporulate.
It is important to remember that the mycelium is adversely affected by lack of moisture inside the log and/or high temperature. The logs must be prevented from drying out inside and from overheating. This can be achieved by keeping them in the shade and watering when necessary. Shade can be natural, as under trees or bushes, or man-made, as under a porch or shade cloth. Dehydration can be avoided by exposure to average rainfall or by manually watering – soaking or sprinkling. During a drought, water the logs on a regular basis – once a week. However, sprinkling logs for short intervals on a regular basis will result in de-barking and will shorten the life of the log. The ideal regime is to soak the logs thoroughly every 6 to 8 weeks to ‘force’ fruiting. This may be accomplished by natural rainfall or by manual soaking or extended sprinkling. The sprinkling/soaking protocols referred to below are management techniques that will protect the integrity of the bark and extend the life of the log.
The integrity of the bark must be maintained because it is the ‘skin’ of the log — it keeps moisture in and other organisms out. The bark is negatively affected by UV rays and by constant wet/dampness. The outside of the log must be allowed to dry to prevent molds from growing on the bark. Therefore the log needs to be in a well-ventilated area and not in standing water such as a swamp. Ideally your log/s should be standing up, with one end on the ground and the other end leaning against a tree, or against a string, rope, or wire that you can string between two trees or posts. Logs can also be stacked against each other in various arrangements. This prevents the mushrooms from getting squashed or dirty as they emerge, and allows the log to absorb some moisture from the ground. The logs should be handled with care as they age and the bark becomes more fragile.
Generally, a log will fruit spontaneously in the spring following rainfall, producing a few mushrooms. To get larger, predictable fruitings the logs must be “forced”. This is achieved by adding moisture to the log. Soaking the whole log in cold water for 6-18 hours (older logs require less soaking as they are more porous) is the best way to accomplish this. However, irrigation with a sprinkler for 24-48 hours also works. The logs must also be physically “shocked”. This can be achieved either by movement during the soaking process, or by dropping them to the ground when you turn them end over end, which you should do periodically if you sprinkle rather than soak. It is worth repeating that the log must be soaked completely through to the sapwood and that the bark must then be allowed to dry out in a well-ventilated area and protected from prolonged periods of direct sunlight.
Approximately a week after soaking or irrigation the logs will start to “flush” with mushrooms. From the time you see little mushroom ‘pins’ coming out, to maturity, depends on the ambient temperature and humidity. Spring and fall growth is usually slow but summer fruitings can mature in a couple of days. The mushrooms should be harvested shortly after the veil has broken under the cap revealing the gills. Following harvesting the logs should be left alone so the mycelium can re-energize itself by digesting more wood lignan. This means six to eight weeks rest and then the soaking/sprinkling can be repeated. Using this management regime the logs can produce 3 to 4 harvests per season yielding up to a total of 1 Kilogram of mushrooms per year. Less frequent soakings, which allows time for the mycelium to store more nutrients between harvests, will generally produce larger mushrooms. With proper care the logs will last an average of five years. Staggered soaking of groups of logs will spread production over your log population.
If you are interested in more detailed information about log inoculation and management these books are excellent:
Growing Shiitake Mushrooms in a Continental Climate by Kozak,M. & J. Krawcyk
Shiitake Grower’s Handbook by Przybylowicz, P. & J.Donaghue
These books may no longer be in print or may be difficult to obtain, and are quite expensive. An excellent source for updated and detailed information about mushroom cultivation outdoors on hardwood logs is the Cornell University website. Here is the link to their interactive website with information about log inoculation and management:
The website has videos and a 56 page manual titled “Best Management Practices for Log-based Shiitake Cultivation in the Northeastern United States” that you can browse and download for free.