How to Initiate Fruiting for Oyster Mushrooms (Beginner Step-by-Step Guide)

How to Initiate Fruiting for Oyster Mushroom Blocks (Step-by-Step)

Whether you made your own oyster mushroom block or bought one online, initiating fruiting is where a lot of beginners start second-guessing themselves. The good news? It's actually pretty straightforward once you understand what the block needs. Here's how to start the fruiting process and get those pins going.

Make Sure Your Block Is Ready

Before you cut into anything, make sure your block is fully colonized and healthy.

A block that's ready to fruit should:

• Be completely white with mycelium

• Feel firm (not overly soft or waterlogged)

• Show no signs of mold or weird discoloration

Once you cut into the bag, give it a quick sniff. Healthy mycelium smells fresh and earthy—kind of mushroomy. If it smells sour, sweet, or rotten, something's off.

Preparing the Block (For Homemade Bags)

If you made your own block, the top will usually have a loose plastic flap and a filter patch where air exchange occurred during colonization.

Before initiating fruiting:

1. Gently squeeze excess air out of the bag.

2. Fold the loose flap down tightly to shape the block.

3. Secure it with micropore tape or regular tape so the block holds its form.

This helps create a firm, stable block for consistent mushroom growth.

Where to Cut the Bag

Once your block is ready, you’ll cut an opening where the mushrooms will grow out.

You can fruit oysters either:

• From the side of the block (most common)

• From the top

• From the front face

All work — the most important thing is consistent humidity and airflow.

Common Cutting Methods

Any of these are effective:

• Small X-shaped cut (most common method)

• Straight horizontal slit

• U-shaped cut

The purpose is simply to expose the mycelium to fresh air and moisture to trigger pin formation.

How to Make the Cut

• Use clean scissors or a sharp blade

• Cut directly into the plastic (not deep into the substrate)

• Keep the slit small (1–2 inches)

• Avoid tearing wide openings

After cutting, you may gently press the block to push humid air toward the opening.

After you cut your opening:

• Gently squeeze out any excess air from the bag

• Fold the plastic flap over the top

• Tape it down with micropore tape if you need to

This keeps airflow controlled while still letting pins form.

Where to Put Your Block

Oyster mushrooms can fruit either out of the side of the bag or upward from the top.

If you're using a Martha tent or grow chamber:
Just place the block inside where it'll get good humidity and fresh air exchange.

If you're fruiting in open air:
Set the block on a counter or shelf and mist the cut area lightly 2–3 times a day. You can also put a humidifier nearby so moisture drifts over the cut without directly soaking the block.

Don't spray water directly into the block. You want humidity around it, not waterlogged substrate.

What Happens Next

Within a few days, you should start seeing small pin clusters forming at the cut site. Once pins show up, just keep the humidity and airflow consistent as they grow into full-size mushrooms.

Depending on your conditions, oysters can go from pins to harvest in just a few days.

Quick Troubleshooting

No pins after several days?

• Try increasing fresh air exchange

• Bump up humidity a bit

• Check if the substrate is too dry or too wet

Mushrooms looking deformed or thin?

• Probably not enough fresh air

Strong unpleasant smell?

• Possible contamination

Final Thoughts

Initiating fruiting doesn't have to be complicated. Once your block is fully colonized, you're basically just giving it the right signals: fresh air, humidity, and space to grow. From there, the mycelium handles the rest.

With a little observation and patience, you'll be harvesting fresh oyster mushrooms before you know it.

Most oyster blocks will produce multiple flushes before they are spent. You can learn more about what to expect over time in our post on how many flushes gourmet mushrooms produce.