What is Agar? When do you need it for mushrooms?

Agar is a gel-like growth medium that can be used to store and grow mycelium and many other living organisms and even tissue cultures. Agar plates are commonly used when trying to isolate healthy and contaminate free cultures from spore prints or syringes. This subsequently reduces that amount of grain spawn that will fall victim to contamination from spore syringes. It’s important to remember that spore prints and syringes are not technically sterile, however by placing these spores onto an agar plate first, healthy mycelium can be isolated and removed to a clean sterile plate. Once established and contaminate free, areas of mycelium that have the traits you are looking for can be isolated. This can lead to very uniform and even growth in a flush, leading to densely packed canopies.
You can probably already see that by using agar, the possibility to experiment by isolating and cloning mycelium for colonising is greatly increased! What fun!

Additionally, as the mycelium on an agar plate is already established and growing, when added to grain spawn, they are significantly quicker to colonise than if a spore syringe was used, and this is in addition to having a lower contamination rate.

Agar preparations can be placed in small containers which can be placed in an autoclave or pressure cooker to sterilise. This provides a sterile surface to place your spores.

The agar provides a two dimensional surface which the mycelium can grow on. Usually food dry will be added. The combination of food dye and a two dimensional surface make identification of contaminants much easier!

In addition to the above perks, Agar is great for the long term storage of your mycelium. Agar plates can be kept for months if stored correctly in a cool dry place or even a fridge that doesn’t have significant temperature changes ( plates cannot be frozen), and then readily taken and added to grain spawn.

How to make agar plates for growing mushrooms

Many methods exist for preparing agar plates, this method below is by far the cheapest and easiest method you can use, all the items you need can readily be found at a supermarket, with no expensive glass agar dishes required!


Small Containers

Hypafix tape, or Micropore tape ( or 0.22 micron adhesive filters)

Drill bit or nail

20grams Agar Agar

1 Litre water

20 grams Dry Malt Extract

Notes of Equipment:

The style of container you use can vary to match what you can find, as long as it has a lid that provides a tight fit. Anything loose that readily falls off, or has clear gaps when applied will not be suitable.

Below are two container that have been used with nil issues, 

This container was bought in a packet of twenty from the reject shop for less than three dollars!

These agar dishes have been in storage for 3 months with no signs of contamination.

Ensure that you do a test run on your containers in your autoclave or steriliser to ensure they hold up to the heat. If they are rated PP5 ( check near the recycle symbol,)  They should be fine. 

MEA can be bought online or from brewery shops, the following can be readily found in Big W. Its not a problem if you cannot find it however as many many alternatives exist. Click here to see all the different possibilities ranging from potatoes to dog food. 

Prepare the Containers

Wash and dry your containers, while they are drying prepare the lids. The Agar will need gas exchange, therefore you need to add a hole in the lid. One hole in the centre ¼ inch. Cover this hole with micropore tape or your adhesive filters.

Prepare the Agar

Bring 1 litre of water to the boil for 5 mins and add your food dye

Measure out 20 grams of MAE and add to the water

Add 20 Grams of Agar Agar

Stir to ensure contents are thoroughly mixed.

Pour the agar

While the Agar is still viscous, carefully pour into each of your containers to a depth of 2-4mm.

Add your lids and allow to set.

Start to prepare your pressure cooker or autoclave.


You will need to sterilise your agar plates as soon as possible after pouring.

To do this, place a piece of aluminum foil over the top of each container, this is to stop excess moisture affecting the tape. 

If using a pressure cooker the process is much the same as for grain jars, place a trivet on the bottom, or jar rims, to lift the jars above the water, add water and bring the pressure cooker to pressure. Cook for 45-60mins. 

Take the pressure cooker off the heat and allow to cool overnight before removing the plates to reduced condensation

Keep the foil on the containers until you are ready to use. Store in a cool dry place, if you live somewhere warm, keep in the fridge. 


Keep your containers for 2 weeks and check for signs of any contamination prior to adding spores or mycelium. This will allow you to be sure that your dishes are free from contam and safe to use!

Agar plates growing mycellium
Agar plates in mycology : source Mycelium Queen https://www.youtube.com/watch?v=SJNX_2T_po4

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