You suspect something is wrong.
That bag of potting soil doesn’t look like it did when you bought it. Or is it just your overactive imagination?
Surely it gets better with age. Or is there the possibility that potting mix can go bad and no longer provide any benefit to your plants?
Or even worse! It might be harmful!
Actually, there’s a tricky threshold between a good and a bad product.
Let’s take a closer look.
Can Potting Soil Go Bad
Potting soil can go bad if not stored properly. It can dry out, clump, develop mold and fungi, and even smell rotten. Using this can introduce disease to plants or starve them of nutrients, water, and oxygen.
To ensure you’re not doing your plants more harm than good, you should confirm whether your potting mix has gone bad or is still usable.
Potting soil consists of a variety of ingredients other than compost. For example, it often contains peat moss and other similar components to enhance the water holding capacity of the product.
All the ingredients are organic, meaning they have the potential to decay to the point that they no longer offer any benefit.
There are several things to think about when considering whether potting soil is going bad. Namely, does it expire, can it lose its nutrient value, and can it spoil. In each instance, it could become unusable on plants.
But all is not necessarily lost! Old potting soil may still be usable, and you may be able to revive it to re-use in your garden. After all… it’s a shame to let something valuable go to waste! Try mixing it with fresh product, or add it to the compost pile to recycle it.
How To Tell If My Potting Soil Is Bad?
There will be some telltale signs that your potting soil is bad. These are warning signals not to use it.
- Pests are attracted to the potting soil. Pests such as gnats, small flies, and other pests flocking to your potting mix indicates that something is amiss in the bag.
- It begins to clump. The peat moss in the potting soil has a limited shelf life of 1 to 2 years. As it decomposes, it becomes denser and loses its ability to hold moisture. It will also make it difficult for plant roots to push through the mixture.
- Mold develops in the potting soil. If it’s inappropriately stored, it can grow mold and fungi, which will attract some of the pests we spoke of earlier.
- A foul smell in the bag. Bacteria and fungi that invade your potting soil will start to decompose the organic material in the mixture. The gasses given off by these organisms will give off a nasty odor.
Why Does My Potting Soil Smell Bad?
The rotting smell is caused by bacteria, fungi, and other microbes attacking the product’s organic material. This can occur if the compost used in the potting soil was not fully matured or other organic matter finds its way into the mix.
As the microbes consume the organic matter, bad-smelling gas is given off, resulting in the rotting smell.
Potting soil should never have a foul odor. Take a whiff of a handful of the good stuff; it will smell rich and earthy, but it will not stink!
Don’t make this mistake – If it has a rotting smell, it means something is wrong and should not be used on your plants (It can introduce disease).
Generally, once the potting soil has become contaminated in this way, it cannot be used or treated. Instead, it should be discarded or recycled in a hot composting system.
Does Opened Potting Soil Go Bad?
Potting soil that has been opened has a greater risk of going bad. This is because it has more exposure to contaminants by pests and undesirable microbes such as fungi and mold spores.
Bags of potting soil must be stored correctly to ensure their longevity and protect them from spoiling. Opened bags can last up to 6-months if stored properly.
Does Unopened Potting Soil Go Bad?
Potting soil is usually sold in plastic bags, and you may mistakenly think this protects it from going off.
If you look closely at the bags, you will notice small holes, usually at the top. These holes allow the product to breathe since many good living organisms and microbes are in the mixture.
While these holes allow the product to breathe, it also allows moisture to escape from the bag, which will cause it to dry out over time.
So does potting soil go bad in the unopened bag?
Instead, it will dry out and lose its nutrient value and water-holding characteristics over time.
Does Potting Soil Have An Expiration Date?
So how long can you store unopened bags of potting soil? Does this product have an expiry date?
Potting soil will reach a point where it starts to degrade. As a result, it will no longer offer the same level of nutrients or soil aeration to be suitable for sustaining your potted plants.
The main component that degrades the fastest is the peat moss added to increase the water retention characteristics. As the peat moss degrades, it becomes more dense and clumpy. Peat moss usually reaches this point in 1 or 2 years.
Most potting soil bags do not have an expiry date stamped on their packaging, but you can expect an unopened bag to last up to 2 years.
It’s best to use the product within a year of purchase since you do not know how long it has been on the shelf at the supplier. Write a date on newly purchased bags so you can keep tabs!
Is Moldy Potting Soil Bad?
When you open a partially used bag of potting soil, you may notice a layer of mold on the surface. This generally occurs if the opened bag isn’t stored correctly.
So can you use this soil, or should you discard it?
The mold will generally develop on the upper layer of the compost. If you can easily scoop the affected layer off the top, you can safely use the rest of the potting mix.
If the mold has spread throughout the bag or too much of the soil to make it worth a rescue attempt, it’s not a good idea to plant anything in it.
Tip: Lay the potting soil on a tarp in the sun to kill the mold and fungi. Then recycle the product in your compost bin.
Is Potting Soil Still Good If It Dries Out?
If the potting mix is not too severely dried out, you can rehydrate it, and it will still be usable. However, suppose it has dehydrated too much. In that case, the microorganisms in the mixture and the water-retaining ingredients will no longer be viable and valuable to your plants.
Potting soil in an opened bag will dry out faster than in an unopened bag.
The value of the nutrients locked in the mixture will also degrade as it dries out. You can not restore the nutrient content simply by rehydrating.
Does Potting Soil Go Bad If It Freezes?
Potting soil should not have a high enough moisture content for the mixture to freeze solid in the wintertime.
Once again, correct storing of your product can prevent it from freezing in low winter temperatures.
After it defrosts and dries out a little, it’s safe to pot your plants, and it will retain most of its beneficial characteristics.
Potting soil is a careful balance of ingredients designed to help seedlings and young plants.
Storing your product the right way will allow you to keep opened bags for up to 6 months and unopened potting mix for 1 to 2 years.