Crimini ~ Portabella Mushroom Growing Kit Instructions

Upon opening the box your kit arrives in you will see:

  • Gallon Ziploc style bag containing casing layer
  • Liner with colonized agaricus substrate
  • And these instructions

What you will need:

  • Large mixing bowl  (4 qt or larger)
  • Measuring cup
  • Spoon (optional – may use clean hand to mix)
  • Spritz bottle
  • 4 cups Water + water for misting
  • An area OUT of direct sunlight and away from direct airflow.  Indirect airflow is fine.

Remove the gallon bag with the casing layer.  Open the liner exposing the substrate.  Pull the liner over the sides of the box.


Get ready to mix your casing layer.  Poor the contents of the Gallon Bag into a large mixing bowl.  Pour 2 cups of warm water over the dry mixture mixing as you go.  Evenly incorporate the water leaving no dry spots or clumps.  Add additional 2 cups of warm water in the same manner.   For a total of four cups of warm water.

Lightly scratch the surface of your colonized substrate.  Remove a loose handful, add it to your casing mixture.  Stir in, being certain that it is evenly distributed and your casing layer has no clumps or dry spots.  If you were to gently squeeze the casing layer it will readily release water between your fingers. 

Lightly pat the loose/scratched substrate back in place. 

Top with casing layer evenly making sure to get to all sides and corners… a nice even layer.  To achieve this we scratch the casing:  fingertips down into the casing moving in a circular motion to evenly distribute the casing to all edges and corners.

Bring plastic liner back up tying the tabs together loosely – offering an air space between the top of the casing and the bag.  Let sit at room temperature for four days (no higher than 85 degrees please).  Be sure that the kit is out of direct sunlight.  Cool dark place like a corner in a closet or basement works well for this stage of "rest".


At the end of the 4th day you will flush your kit.  To do this, simply open the plastic, pulling it over the sides of the box.  Mist lightly with your spritz bottle and Cold water.  This shocks the mushrooms to start producing "pins".  Pins are formed by the mycelium strands coming together.  They appear as white dots on and in the casing layer.  Not all pins will fully develop into mushrooms.  However, you do not get a second chance at "pinning".  Whatever you see develop over the next 5-7 days is what can potentially grow into mushrooms. 

During this week of devoloping pins, mist daily.  Keeping your casing layer moist, looking as it was the day of casing.  Be sure your kit is not exposed to direct sunlight or direct airflow.  Imagine a forest full of lush vegetation in spring… it is neither bright and sunny nor dry.  Instead it is moist and dimly light due to the trees above… with light rustling breezes.  This is what your mushrooms would like.  Some people use a basement (with a fan moving air indirectly throughout), others a rarely used bathroom or even a closet.  Wherever you choose be sure your kit is easily accessible from this point on.


Approximately Day 7 after casing begins the “Growing” portion.  As the pins begin to develop into mushrooms you will stop watering.  Do not water on mushrooms as this may result in brown spots on your mushrooms.  Your mushrooms will double in size every 24 hours.

Once your mushrooms have grown to a size you wish to harvest you may do so by “breaking” them off the bed.  Gently hold the cap – twist and tilt leaving the casing layer beneath undisturbed so the pins inside have a chance to grow.  You will pick over a 2-3 day period.

Once your “First Break” is picked off, start to mist your kit heavily being certain to bring/keep moisture up in the casing layer, similar to the moisture at the time of casing.  Do this daily for the next 3-4 days.  At which time you will start to see your “second break” emerge.  Once you see the second set of mushrooms emerging pause watering/misting through the time they are growing.   Harvest as each mushroom is ready, over a 2-3 day period.

Once the “second break” is off… again, water/mist for 3-5 days.  It is normal for it to take a bit longer for the kit to bounce back after the second break than it did after the first break.  Again, pause watering while the mushrooms are growing and harvest when ready.

At this point you may try for a fourth or consecutive breaks.  However, you will see fewer and fewer mushrooms.  On our farm, we dump the compost out of our trays after the third break, mix the casing into the growing layer and then use the “spent compost” in our gardens, around trees and shrubs and to feed our house plants.

Visit: ~ “Crimini Kits” tab under Mushroom Growing Kits for photos and additional information. 


Happy Mushrooming!

The Semyck Family of Willow Mountain Mushrooms

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