Emily Johnson
When it comes to cultivating mushrooms, straw logs are an easy and rewarding method. The size of the straw log is an important consideration, as it can impact the success of mushroom growth. While any size log can be used, with smaller logs colonizing faster, the ideal size for a straw log is about 10.5 inches thick. This ensures adequate airflow, as larger logs can develop an anaerobic core due to a lack of oxygen, leading to contamination. To achieve this ideal thickness, poly tubing with a 16 lay-flat diameter is recommended.
| Characteristics | Values |
|---|---|
| Container type | Poly tubing |
| Container diameter | 16" lay-flat |
| Container thickness | At least 4 mill |
| Log thickness | 10.5 inches |
| Straw weight | 30 lbs |
| Spawn weight | 3-6 lbs |
| Spawn ratio | At least 10% |
| Colonization time | 7-14 days |
| Drilling diameter | 4-6" |
| Drilling length | 3-4' |
| Totem method diameter | Up to 12" |
| Totem method height | 6-18" |
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What You'll Learn
The best containers for straw logs
Using poly tubing with a 16″ lay-flat diameter will give you a log about 10.5 inches thick, which is a perfect size. Going with a larger diameter will cause an anaerobic core, which will eventually contaminate the log.
To use poly tubing, tie one end of the tubing with wire or a zip tie. Then, stuff the straw and spawn mixture into the tubing one handful at a time, pressing down and packing the straw tightly as you go. This will prevent air pockets from forming between the straw and the tubing. Once the log is the desired length, force all the air out of the log by pressing down hard and twisting the top of the tubing. Tie off the top again with wire or a zip tie. Finally, punch holes into the side of the log to allow it to breathe and for colonisation to occur.
Another option for a fruiting container is a 5-gallon bucket with holes drilled into the sides. You can also use a large drum, which can be used with a propane burner for pasteurisation.
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Pasteurizing straw
Straw pasteurization is necessary if you want to start growing certain types of mushrooms on your own. Pasteurization is the process of reducing the number of microscopic competitors in a substrate (in this case, straw) to give the mycelium (the fungus that produces mushrooms) an advantage over harmful organisms.
Types of Straw
Cereal straws (not hay) such as oat or wheat straw are used as a base for mycelium growth.
Cutting the Straw
Before pasteurizing, cut your straw into 1-3 inch segments. This can be done with a lawnmower, blender, or any other machine suitable for the job. Mycelium will colonize smaller pieces of straw faster and more easily, resulting in faster colonization and a bigger yield.
Hot Water Pasteurization
The most common method of pasteurization is to soak the straw in hot water. The straw should be soaked in water heated to between 65-82 °C for 1-2 hours. The water should be drained, and the straw should be cooled before mixing in the mushroom grain spawn.
Cold Water Lime Pasteurization
This is a low-tech, cheap, and effective method of pasteurizing straw. The process involves soaking the straw for 12-24 hours in a bath of cold water that has been treated with hydrated lime. The lime increases the pH of the water, killing off mold spores, bacteria, and other contaminants in the straw. Once drained, the straw can be inoculated with mushroom spawn, and the mycelium will grow unhindered.
Other Methods
Other methods of pasteurization include simply soaking the straw in water, draining it, and placing it in a sealed container. If properly sealed, the aerobic contaminants will die off, and the anaerobic contaminants will proliferate. When the container is opened and the substrate is exposed to the air, the anaerobic contaminants will die off, leaving no aerobic contaminants. This method can also be done with laundry detergent or dish soap. Wood ash can also be used in place of lime or other chemicals to pasteurize straw by raising the pH of the water.
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Types of spawn
The size of straw logs for mushroom cultivation varies depending on the type of tubing used and the desired thickness of the log. Using poly tubing with a 16-inch lay-flat diameter will result in a log that is about 10.5 inches thick, which is considered a suitable size. Creating a thicker log can lead to the development of an anaerobic core, causing contamination.
Now, let's discuss the different types of spawn:
Plug Spawn
Plug spawn is created by growing mushroom mycelium on wooden dowels, which are then hammered into holes drilled in freshly cut hardwood logs. The holes are then sealed with melted wax. This type of spawn is ideal for outdoor cultivation, especially in cold climates, and is perfect for small projects or beginners. Plug spawn is simple to use and requires no special tools beyond a hand drill. It is slightly more expensive than sawdust spawn and takes longer to colonize a log. However, it is excellent for shipping and transporting. Common varieties of plug spawn include Blue Oyster, Golden Oyster, Italian Oyster, and Lion's Mane.
Sawdust Spawn
Sawdust spawn consists of mycelium grown into hardwood sawdust. It is the most common type of spawn used for outdoor mushroom production and is the preferred choice for many commercial growers. Sawdust spawn is relatively inexpensive, reliable, and colonizes faster than plug spawn. It is often used for inoculating logs for consecutive years, making it a cost-effective option for long-term projects.
Grain Spawn
Grain spawn is created by growing mushroom mycelium into certified organic rye or millet grain. It is primarily used for indoor mushroom cultivation, particularly in commercial settings. Grain spawn is ideal for inoculating sterilized or pasteurized substrates and can be used to add additional nutrients to the substrate. This type of spawn is not suitable for outdoor log inoculation. It is often used for Oyster, Lion's Mane, and Shiitake mushroom cultivation and plays a crucial role in fungal restoration programs.
These three types of spawn offer different advantages depending on the specific needs of the cultivator, the desired mushroom variety, and the growing environment. It is important to choose the appropriate spawn type to ensure successful mushroom cultivation.
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How to prevent contamination
Using poly tubing with a 16-inch lay-flat diameter will give you a straw log that is about 10.5 inches thick, which is a good size. If the log is too thick, it will likely become contaminated from the center out due to a lack of air.
To prevent contamination, it is important to follow these steps:
- Ensure your workstation is clean and well-ventilated. Dirty air can cause contamination.
- Prevent air pockets from forming between the straw and the tubing by packing the straw tightly. This will also prevent mushrooms from pinning under the plastic.
- Punch holes into the side of the log to allow the mushroom log to breathe and for colonisation to occur.
- Avoid overwatering your logs, as frequent light watering can damage logs and cause contaminant growth. Instead, opt for long periodic soaking of no more than 24 hours if your logs appear dry.
- Seal the holes in your logs with food-grade wax to prevent contamination by competing fungi species and to lock in moisture.
- If growing your mushrooms outdoors, use barriers such as fencing to protect your logs from pests like squirrels, chipmunks, and deer.
- To prevent slug and beetle infestations, some people use greenhouse fabric under their logs, set up beer traps, or periodically remove the slugs and find them a new home.
By following these steps, you can effectively prevent contamination when cultivating mushrooms using straw logs.
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Choosing the right tree species
While mushrooms are flexible organisms that can grow on a variety of trees, each mushroom species has a preferred type of wood. Matching the mushroom to the correct log species will produce a higher or more consistent yield.
As a general rule, most edible mushrooms grow on deciduous hardwood trees. Poplars and other soft hardwoods will colonize faster and produce mushrooms sooner, but they don't yield as much or produce for as many years. That being said, oyster mushrooms will be more successful on poplars and aspens than oaks or maples.
Italian oyster (Pleurotus pulmonarius) can grow on some pine family trees, though flushes will be smaller or less frequent than on hardwoods. King oysters will also grow well on straw. If you're cultivating Hemlock Reishi (Ganoderma tsugae), you can use coniferous wood.
Shiitake, Oyster, Lion's Mane, Comb Tooth, Reishi, Olive Oysterling, Nameko, Chestnut, Turkey Tail, Maitake, Chicken of the Woods, and Brick Cap all grow on wood logs. However, Maitake, Chicken of the Woods, and Brick Cap grow best when the log is treated prior to planting, either by sterilization, steaming, or boiling.
Logs should be inoculated within four weeks of cutting. If you wait longer, your mycelium will have to outcompete the other fungi that have already started colonizing the log.
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Frequently asked questions
A 16″ lay flat diameter will give you a log about 10.5 inches thick, which is a perfect size. Going too much bigger will cause an anaerobic core, eventually causing the log to contaminate.
You can make the log any length you want. However, you don't want the logs to be so large or heavy that they are difficult to use.
Small-diameter wood will colonize faster, but will not produce for as many seasons as a larger log. For drilling methods, a 4-6’’ diameter with a 3-4’ length is ideal.
King Oysters will grow well on straw, but they may take a little longer to fruit. This species tends to produce large individual mushrooms rather than clusters.
If the log is too thick, it will often contaminate from the centre out, since it will be starved for air. I suggest you try a few different sizes and see what you like to use.
