Overall, the answer to the question does potting soil go bad would be a no. I’m pretty sure that’s a reassuring answer and, for the most part, all you need to know is that potting soil doesn’t usually go bad.
But I’ll offer a more in-depth analysis, revealing how you can tell if your unused potting soil has gone bad or how you can restore it so that you can make full use of it without needing to buy another bag.
If you’re like me and you hate wasting anything, knowing the complete answer to the question does potting soil go bad will be pretty important.
Table of Contents
Does Potting Soil Go Bad? The Debate
In order to understand which are the facts that might be up for a debate, there’s one question to answer.
Does potting soil have an expiration date? We’re definitely prone to throwing in the trash anything that has reached its expiration date but what about this particular case? It’s not like we’re going to eat the expired soil.
It is said that unused potting soil has about 6 months until it reaches its expiration date. What is supposed to happen once these 6 months have passes?
It will start degrading in quality.
When it comes to used potting soil, the recommendation is to change it once a year or once every 2 years.
Judging by this information, the answer to the question does potting soil go bad would be a yes and it must be said that it can go bad quite quickly.
My counter-argument in this debate is this: after 6 months the quality of the potting soil or potting mix might begin to decrease but that doesn’t automatically imply that it’s gone completely bad.
It is safe to say that the quality can definitely diminish but it’s also safe to say that it doesn’t go bad, most of the time.
It can be rejuvenated but if you want to avoid any complications, the obvious choice is to buy a new fresh bag.
Let’s see how you can tell if your potting soil has gone bad or not. Forget about that expiration date and just analyze what’s in front of you.
Does Potting Soil Go Bad? The Signs
Let’s say you have had a bag of potting soil or potting mix for a year or a couple of years and there was no need for you to use it before now. Maybe you overestimated and bought too much and you just kept it on for when you might need it but that has been a couple of years back.
The soil might not be completely unusable but it might not be as good as a fresh one at providing the plants with the moisture content, nutrient levels, and support that they need.
Are there any circumstances that might make you think that your potting soil has gone bad and there’s now a need for spending money on a new fresh bag of potting mix or potting soil?
There are a few signs to indicate that a bag of potting soil has gone bad and it’s pretty much unusable:
- bad smell – the easiest way to tell that the potting soil has gone bad is if it smells of rotten eggs
- mold growing in the soil – simply let the soil dry out in the sun if you can spread it out outside somewhere
- it is basically surrounded by insects (fungus gnat infestation) – you can kill the adult gnats by using insecticide if you have no problem with it and the larvae can be killed by spreading out the soil and letting it out in the sun for a few days
- dense and compact in appearance, a dustier consistency
- infected through some disease
The Simplest Solution
If you don’ want to take absolutely any risk and you’re in the situation where you ask yourself does potting soil go bad, the easiest solution would be to just buy a bag of fresh potting soil or potting mix and ensure the complete success of your crop.
That’s definitely a quick solution if there’s not a big quantity that needs to be replaced and the easiest, although pricey.
Potting Soil Rejuvenation Guide
I might have you confused with my no and yes answer to the question does potting soil go bad but there’s on quick fix to all of that: rejuvenation.
Unused potting soil rejuvenation
With older unused potting soil there’s a loss of:
- nutrients – the levels will decrease the longer the soil is stored, even if the potting soil is stored correctly, less nutrients means less plant growth
Let’s talk about potting soil rejuvenation. This is how you can offer it a second life and put it to good use:
- an old potting soil that hasn’t been used fresh can be rejuvenated by adding nutrients – you can use compost, worm castings, granulated organic fertilizer
- if the soil smells bad and it’s damp, spread it out on a plastic tarp and let it dry out in the sun, the smell should disappear in a day, once the bacteria has been killed
- if you’re dealing with compact soil, add some coco coir to provide lightness – it works in a 1:1 ratio
Unfortunately, most methods for rejuvenation involve the need for open space and warm sunny days.
Used potting soil rejuvenated in a few steps
The easiest way is to combine the old soil with a third of new potting mix and maybe add a bit of compost.
That’s all you have to do if you weren’t growing heavy feeder plants and you haven’t had any issues with the soil.
The more elaborate option:
- spread out the soil and see if there is any plant debris or roots – those need to be removed
- run water through it to remove excess salts
- mix it with fresh compost in a 1:1 ratio
- to each 1 gallon of soil you can add a light dusting of gypsum and lime and 1 tablespoon of general purpose fertilizer, as sfgate.com suggests
How to Store Potting Soil Properly
Properly stored potting soil will be a big factor in answering the question does potting soil go bad. If you have stored it properly, you have a high chance of being able to use it.
The best storage method is in lidded containers away from heat and high humidity. It’s definitely similar to storing flour.
- tightly close the bag – if peat moss gets wet it’s highly likely that it will decompose
- place it in plastic bins
- in order to limit bacterial growth in the soil, store the bins safely, away from rain and sun
- an unopened bag can be good for 1-2 years – the information can also be provided by a best by date
- an opened bag will take 6 months before starting to slowly degrade but it won’t go bad, it just slowly decreases in quality
Using Good Potting Soil Is Crucial
It’s absolutely imperative to know if your potting soil has gone bad because this is the component that provides plants with the needed nutrients, moisture, and structure for a normal plentiful growth.
Potting soil is usually a medium used for growing plants in pots and containers.
Potting soil can be mixed with garden soil to be used in gardens, especially for those who make raised beds. But it’s not compulsory to do that because plants grown in garden soil are already exposed to an open environment that provides them with everything they need from nutrients to proper support, natural drainage, and direct sunlight.
Contrary to what the name might say, potting soil usually doesn’t even contain any soil. It can contain soil but more often than not it’s completely soilless. It’s what we refer to as soilless mixes.
Potting soil composition
- peat moss – for moisture and nutrients retention
- pine bark – used more for its anchorage benefits but it also has moisture retention and aeration properties
- perlite or vermiculite – makes the soil less dense and heavy, provides additional air space
If you know about hydroponics systems, you’ll know that perlite, vermiculite, peat moss, and pine bark are all growing media for hydroponics.
The addition of coco coir is not unusual either. It’s an excellent growth medium.
Speaking of soilless mixes, that’s the main difference between potting soil and potting mix: potting mix doesn’t ever contain any soil, it’s always a soilless mix.
It’s not unusual to use the two forms interchangeably because nowadays they pretty much contain the same things.
The only difference is that on some it says potting mix while on others it says potting soil. Their composition is very similar and that’s why they’re interchangeable and the answer to the question does potting soil go bad applies to both.