GUS grow guide

Before you dive in, review the GUS instructions to get started.


From the mushroom cultivation classics to the visually delicious, we have curated a list of our favorite fungi-focussed reads.


Learn what to look for and when to harvest


Blue Oyster: Young Stage Primordia.

Behold, the first signs of life! At this stage the mushroom needs the most moisture and is at high risk of drying out. These mushrooms will likely mature in 3-7 days.

Blue Oyster: Primordia

You will notice the mushroom pins begin to show the famous blue hue. At this stage you will be able to see the fruiting body begin to form, such as the gills and cap. Still small and delicate, be sure not to forget to spritz. These mushrooms will mature in around 3-5 days

Blue Oyster: Young Fruiting Bodies

This is when the blue oyster mushroom is at its most vibrant and rich in color. Although not ready for harvest, it's iconic blue glow is very photogenic and fun to admire. These mushrooms will mature in as little as 12-36 hours!

Blue Oyster: HARVEST READY Mature Fruiting Bodies

These mushrooms are ready for harvest! You will notice that the color has turned from blue to brown but is still deep in color and the edges of the caps are still downturned. Spores will begin to release at the end of this stage so catch them quick and pick them!

Blue Oyster: Past it's Prime

If your mushrooms have flattened out and have faded in color but feature dark edges, you have waited a little too long to harvest. While this stage is less desirable in texture and flavor for cooking it is still completely edible as long as it doesn't appear dry and wrinkled. Once the mushroom has started to dry out it is best to use them to make a mushroom stock.


Golden Oyster: Primordia

Even though it looks like a piece of gum someone stuck under a table, soon this blob will be a majestic golden beauty. At this stage, your mushrooms mature in about 2-3 days. This is when your mushrooms needs the most moisture and are at higher risk of drying out.

Golden Oyster: Young Fruiting Bodies.

We think golden oysters look kind of like popcorn at this stage. It won't be long before the mushroom is mature, around 24-48 hours. Be patient ...or set up a time-lapse!

Golden Oyster: Mid cycle fruiting bodies

The caps now defined and range from the size of a dime to the size of a quarter. They are almost perfectly round and very cute. At this stage, your mushrooms will mature in around 12-24 hours.

Golden Oyster: HARVEST READY Mature Fruiting Bodies

These mushrooms are ready for harvest! You will notice that the caps are still slightly downturned, velvety, wide and not yet browning or drying out. A few spores may have started to drop but not many. Hurry and harvest these now!

Golden Oyster: Past their prime

If your mushrooms look like this, then unfortunately, you have waited too long to harvest. Some of the mushrooms around the edge of the cluster are now dried out, wrinkles and browning has begun. They are dusty from their spores. Golden oysters need to be eaten fresh and at this stage they are best used for cooking only in a mushroom stock.

THE BASICS: Getting Started with GUS.

1. Get your fruiting blocks:

We recommend mushroom fruiting blocks from North Spore, our mushroom farm partner. North Spore fruiting blocks are high quality and have the best size compatibility with GUS. We suggest first-time mushroom growers start with golden oyster mushrooms. Pink oyster and blue oyster are also suitable for beginners. Be sure to select fruiting blocks and not spray-and-grow kits. Spray-and-grow kits are small in size and not compatible with GUS.
Get your fruiting blocks at

2. Plan your grow:

Once started, it may take anywhere from 2 - 7 days to notice the first signs of life, in the form of tiny mushrooms, called pins or primordia. Once the pins start to form, your mushroom will grow very fast, and will be ready to harvest in around 3-5 days. It is best to plan your mushroom grow for a week when you will not be traveling. We like to recommend that you have a 7-10 day window from start to finish, where you’re at home at least once a day to mist GUS.

3. Place fruiting block into GUS:

Do not remove fruiting block from the plastic bag. Once you received your fruiting block, examine it to see which side has the most mycelium (for most mushrooms, you will notice a white color, for pink oysters you, should see some pink color.) This will be the side you will line up with the circular opening of GUS. Carefully place the fruiting block into GUS. Place the riser brick under the fruiting block if more height is needed. Cut an X in the plastic across the center of the circular opening with scissors. Using a spray bottle, mist the exposed grow medium with water around 10-20 times to start.

4. Choose a growing location for GUS:

GUS was designed to live on your kitchen counter. The kitchen is somewhere you will frequent throughout the day and be reminded to give GUS a little misting, and enjoy seeing the mushrooms progress throughout the day. Place GUS in a well ventilated area with a surface that is tolerant to moisture, such as a kitchen counter top. Mushrooms do well in a room with light but you must keepGUS out of harsh direct sunlight and way from direct heat sources as this will dry the mushrooms out.

5. Mist GUS twice a day:

Be generous with bath time. Each time you mist, spray 5-7 times. Once the mushrooms have begun to form, mist around the mushroom rather than directly soaking it. We recommend misting the growing medium in the opening and the ceramic surface around the opening. This will provide moisture through passive evaporation. In dry environments mist more often.

6. Watch GUS grow:

Our favorite part of growing mushrooms is the excitement of getting out of bed each morning to see how much your mushroom has grown overnight. Mushrooms grow so fast that they will change size, shape, and color throughout the course of a single day. 

7. Harvest:

To harvest, grab firmly around the base of the mushrooms  and twist. Timing your harvest is very important. There is a sweet spot when the mushrooms are full in size, but haven’t yet begun to release spores. Getting this timing right is a learned skill. If you observe a dust under the mushroom and around GUS, it is definitely time to harvest. As you gain more experience, your goal should be to harvest prior to the spore stage.

8. Prepare mushrooms for cooking: 

Do not wash your mushrooms! Washing is unnecessary and can ruin the mushroom’s texture by water-logging it. Cut or lightly brush off any of the remaining grow medium. Remove tough parts of the stem. Once growing medium is removed, you can save the  tough areas of the mushroom that you won’t be cooking and use it to make a mushroom stock.

8. Cleaning GUS and preparing for your next grow:

Carefully and thoroughly wash GUS with hot water and a soft sponge or towel. Some soaps and cleaners may stain or damage the surface of the ceramic. Be sure to clean and rinse away any debris from the last grow as soon as you harvest. This will reduce the risk of letting contamination set in from growing substrate left out for too long. Store in a dry location between grows.

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