Holes in the block should be made as soon as possible after inoculation, as growing mycelium breathes actively and cannot develop well without proper gas exchange in the substrate.
If you’re making the substrate yourself, it’s best to perforate it the same day as inoculation, after hanging it in the incubator.
If cuts aren’t made within two days, mycelium activity decreases. Mold spores and bacteria, which require less air, may begin to thrive, potentially spoiling the mushroom blocks.
Through the perforations, the growing mycelium takes in oxygen and releases carbon dioxide and moisture. However, too many holes can cause the substrate to lose excessive moisture.
About incubation of mushroom blocks
How to make perforations in mushroom blocks.
Round holes in the block are typically made with a punch, which is a round metal tube sharply sharpened on one end. Its diameter is 2.5-3 cm (1-1.2 inches). Often, the punch is not only sharpened but has sharp, toothed edges.
For longitudinal cuts, a utility knife works best, breaking off the blade after every 20-30 blocks to keep it sharp.
Cross-shaped holes are also made with a utility knife. These cuts are recommended so the “petals” of the hole cover the opening and prevent it from drying out.
However, it is better to maintain the necessary conditions for incubation than to rely on “protective” measures. Covering holes with petals can restrict the mycelium’s air supply, slowing its development.
The inner side of the "petals" can also accumulate condensation, which can drip onto the mycelial hyphae, causing its cells to die.
The number of perforations in a mushroom block depends on its weight and dimensions.
It’s also helpful to consider the size of the perforations for effective gas exchange.
Common Cutting Techniques:
Typically, 7-8 round holes are made on two opposite sides of the block. These are about 1.5 - 2 cm (0.6 - 0.8 in) in diameter.
For example, in the image above, you see a 14-15 kg (31-33 lb) block with one-sided perforation totaling 21 holes, which could be reduced to 18-19 while still achieving good substrate overgrowth. At this facility, smaller oyster mushroom clusters are prioritized, requiring more but smaller formations.
- Cut 4-5 slits on each side, each about 5-7 cm (2-2.7 in) long. Avoid making them too large, as the plastic film may tear along the cut.
- Slits are best cut vertically or at a slight diagonal (in a “herringbone” style), as shown in the photo above.
If your blocks are incubated hanging vertically with vertical cuts, and you later place them horizontally in the grow room, the cuts will naturally become horizontal. However, this won't affect the growth of mushroom clusters — they will grow just as well as if you had hung the blocks vertically in the grow room.
In the image shown, you’ll see a batch of bags with vertical cuts, which were hung in one chamber and tied horizontally in another.
In the image shown (click to enlarge), you’ll see a batch of bags with vertical cuts, which were hung in one chamber and tied horizontally in another.
For growing chambers with one-sided perforation, the opposite side of the block often has microperforations — tiny holes about 1 mm in diameter across the film’s surface.
For bags with diameters up to 22 cm (8.6 in), microperforation isn’t necessary, as gas exchange remains sufficient.
When the mycelium attempts to grow through microperforations, primordia can form but die due to insufficient space.
Therefore, with one-sided perforation, bags should ideally be between 19-22 cm (7.5-8.6 in) in diameter to avoid microperforation.
Advantages of One-Sided Perforation
One-sided perforation can be efficient, allowing for double rows in the chamber, which saves space without affecting yield for bags with diameters up to 22 cm (8.6 in).
While some suggest waiting 2-3 days until the mycelium “fluffs up” before perforating to give it an advantage over contaminants, experience shows that delayed perforation can decrease yield.
However, you can also conduct a couple of experiments, and choose the option that suits you.
If there are too many holes, moisture may evaporate quickly, potentially reducing yield, especially in drier substrates. Conversely, if the substrate is overly moist, creating extra perforations may help to moderate the moisture content, improving block quality.
If the oyster mushroom primordia are starting to develop in the vents but most of the pins are still covered by the plastic, you can cut the plastic film.
Use a sharp utility knife to gently lift the film without damaging the pins, and make additional cuts to free the clusters trapped by the plastic.
No, it doesn’t.
Round holes result in fewer mushrooms per cluster, and they weigh less than those formed with a knife.
However, since there are more round holes in the bags, the total weight of all harvested clusters remains the same.
After the first harvest, a dense mass may remain in the perforations, especially when turning the oyster mushroom clusters on a straw substrate. Details in this article
Read about Oyster mushroom yield
