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How to store potting mix?

Just Starting Out

How to store potting mix?

Hi, What do people use to store opened and unopened bags of potting mix? I have a tiny under cover area to use 1x1m. 

I find just using bags often results in the potting mix going mouldy no matter how well sealed. Admittedly until now this has not been in the new under cover area. 

I’d love to know specific names of products used. I’m thinking large plastic tubs. That are water tight but not air tight. Any views? Some say they should be air tight but I’d think that would encourage mold. 

Thank you, 



Bunnings Team Member
Bunnings Team Member

Re: How to store potting mix?

Hello @joanholt49 


Thanks for sharing your question about storing potting mix. A sealed potting mix bag usually has a shelf life of 1 to 2 years max. But once the bag is opened it comes down to 6 moths to one year if properly stored.


The open bag by itself is not enough to keep the microbes at bay. In order to keep the potting mix preserved, I suggest using a Handy Pail 11L Pail With Lid. The 11.1 litre volume is ideal for a wide range of storage applications around the home, garden, shed, workshop or kitchen. This Pail is food grade certified making it suitable for commercial use.


It is leak proof and provides an adequate seal from the outside air thereby slowing down the decomposition process of the soil. Just keep in mind to store it in a dark space away from direct sunlight.


If you have any other questions we can help with, please let us know.




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Community Manager
Community Manager

Re: How to store potting mix?

Thanks for your question @joanholt49


I just wanted to add to Eric's reply that we recently asked one of our most experienced and knowledgable members @Noelle the question how long can you keep potting mix. Noelle says to be careful if the bag is stored for an extended period (more than 6-8 weeks) after purchase as the build up of nutrients can be sufficient to burn the tender young roots of plants, especially seedlings. It is better for your plants to buy what you need, when you need it.




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Kind of a Big Deal

Re: How to store potting mix?

Hi @joanholt49 


Potting mix bags are not airtight nor are they completely sealed.  They generally have a row of breather holes across the top to allow entry of oxygen.  Potting mixes are usually made from composted ingredients and the composting process continues in the bag after manufacture. Air circulation is essential. If the bag is airtight, the mix quickly runs out of available oxygen (or access to it) and tends to rot or putrify, rather than compost, resulting in smelly, sometimes slimy and mouldy, contents. That's why manufacturers recommend buying only what you need and not storing open or unopened bags for extended periods.


The other issue, which Jason has mentioned, is the release and build up of nutrients from the controlled or slow release fertilisers included in most modern potting mixes.  These start releasing their nutrient load as soon as they are added to the bulk mix prior to bagging.  If a bag is stored for an extended period of time (several months), the free nutrients remain captured in the bag and may build up to high levels.


When a fresh bag is opened and used within 2-3 weeks of purchase, the nutrient load will not be high and any available nutrients not taken up by plants will be drained out of pots after watering.

Becoming a Leader

Re: How to store potting mix?

A simple question @joanholt49 - I bet a lot of people want to know about this. Some great responses. I just wanted to reinforce:

1. Keep it dry,

2. Keep it away from the sun and

3. Keep it cool. 

I use this one - - it's a bit bigger but I put my potting mix in it and also other open bags of Orchid Mix etc. It sits under our potting bench mix so easily accessible and protected from the elements. 

In truth - my potting bench is a garage work bench - but works just great for what we use it for. u/pinnacle-1405-x-1100-x-540mm-compact-garage-workbench_p2760256


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