How to Grow a Second Flush of Oyster Mushrooms: The Complete Guide

Table of Contents

1. What are mushroom flushes?
2. How to initiate second flush?
   - a healthy second harvest
   - cleaning the holes: a crucial step
   - prohibited actions: what NOT to do
3. Stimulating Growth in Single-Zone Systems
4. How Many Flushes Can You Actually Get?
5. The "Winter Reset" Hack

What are mushroom flushes?

When the mycelium is ready to bear fruit, it forms primordia, from which single mushrooms or clusters grow.

This is called the "first flush."

In Ukraine, we often call these flushes "waves" (Ukrainian word "хвилі"). I think this name is perfect—it’s like the ocean: a wave appears near the shore, then disappears, only to return again after a short rest.

Mushrooms follow the exact same rhythm. After the first harvest, the mycelium needs time to rest and recover before it starts producing the "second flush" (the second wave). 🌊

How to initiate second flush?

To get a healthy second harvest, you need to help the mycelium "find its way" back to the light.

First, inspect the slits in your bags. If you see dense, white pieces of mushroom tissue sticking out, they must be carefully cleaned.

▶️We do this for two reasons:

1. So the mycelium can grow toward the perforations faster.
2. To prevent mold from settling on the remains of the old mushroom "butts."

💡Note: You do not need to make new slits for the second harvest. The mycelium is perfectly capable of fruiting through the existing holes.

How to clean the holes in the mushroom blocks?

The best time to remove that compacted white lump is immediately during the first harvest. If you are in a rush to get your goods to the market, find time later that same day. The sooner you clean the holes, the faster the new primordia will appear.

💡Note: Do not touch the substrate itself. If some straw is sticking out, simply press it back or carefully trim the protruding part while holding the film flat against the block.

Prohibited Actions: What NOT to Do

I often see growers making mistakes that kill the second wave before it even starts.

✅Avoid these four things:

1. Don't move blocks to the incubator: You risk infecting the entire room. There are far more spores and microorganisms in the growing room than in a clean incubator.
2. Don't seal the slits: Some think the block needs to be "closed" to rest.
   ⚠️This is wrong! The mycelium breathes through those holes. If you seal them, it will suffocate.
3. Don't water the holes with a hose: Never pour water directly into the slits after cutting mushrooms. It won't "rehydrate" the mycelium; it will only lead to rot and mold.
4. Don't remove the film: While this works for Shiitake, it is a disaster for Oyster mushrooms. Without the film, the outer layer of the substrate dries out instantly, and you will get zero mushrooms.

Stimulating Growth in Single-Zone Systems

If you don't have separate rooms and use a single-zone system, you can "trick" the mycelium into a faster recovery by mimicking incubation conditions:

• Temperature: Raise it to 19-20°C (66-68°F) for 3–4 days.
• Humidity: Maintain it at 90-91%.
  ⚠️If you notice droplets of condensation forming on the slits at this humidity level, you must lower it immediately to 88–89%. Keep a close eye on the perforations—they must stay damp but never "drown" in liquid water, as this will suffocate the recovering mycelium.
• Light: If all clusters are picked and no new pins are visible, turn off the lights.
  ▶️Mycelium doesn't need light during this "rest" phase.

On the 5th day, begin to gradually cool the air and lower the humidity back to optimal growing levels. Within 2–3 days, you should see the start of the next wave.

📌What is a "single-zone growing system"?

How Many Flushes Can You Actually Get?

Modern intensive strains are designed to give their maximum potential during the first flush (usually 22-25% yield).

Many large farms only take one or two flushes. Why? Because keeping a room running for a weak 3–5% second harvest is often not profitable.
If your first flush was massive, the second one will likely be small.

However, if your first flush was weak (10-15%) due to climate issues, the second flush might be just as large as the first, provided you have fixed the climate problems (especially those "yo-yo" humidity fluctuations!).

📌Read about the reasons for the death of pins.

After the third harvest, the substrate has usually exhausted its nutrients. At this point, it’s best to send the waste mass to a compost pit to create high-quality vermicompost and have additional benefits.

Pro Tip: The "Winter Reset" Hack

If you live in a region with cold winters, here is a professional trick that many growers don't know about.
If your first flush was massive (over 20%) and you feel that keeping the blocks in the climate-controlled room for a weak second wave isn't profitable—move them outside.
Place the bags in a shady spot and let them freeze.

💡Don't worry, the mycelium won't die; it just goes into deep hibernation.

In the spring, as the air warms up, the mycelium "awakens" with incredible energy.

After being exposed to the frost, the second flush often produces clusters that are much heavier, denser, and more beautiful than if they had stayed indoors.

In some cases, this "outdoor" second harvest can give you an additional 10-12% yield, provided the substrate still has enough moisture and nutrients.

Often this effect can be observed on the third flush, if you collected the first two flushes in the growing room.

Emoji guide: 📌 link | ✅ advice | ▶️ fact | 💡 important | ⚠️ warning