After months or even years, you might wonder if potting soil can expire. You might hesitate to use this for your garden, but the truth is, potting soil doesn’t go bad. But there are some key things to look out for.
In general, potting soil has no expiration date. If stored properly, it can be kept for many years. But soil quality will naturally decay over time so it is best used within 1-2 years. When the soil is exposed and unprotected, insect infestations and potential mold growth are likely.
When you garden a lot, it’s no surprise to see those bags of potting soil start to stack up. But do they have a shelf life you have to worry about? Let’s unearth this together, and keep on reading!
On average, packaged potting soil does not expire but may contain organic matter like peat moss that could affect the overall texture and quality of the soil. The soil will naturally degrade over time. It is best to use packed potting soil within the first 2 years it is opened.
Despite the name, potting soil contains very little soil. It is actually a huge blend of diverse ingredients and organic matter to help provide your plants with the right environment and nutrients they need.
What may concern some gardeners, however, is the use of peat moss in commercial potting mixes. Peat moss is a very popular soil amendment that slowly decomposes over 1-2 years and may eventually influence the overall nutrient level and texture of the potting soil.
As soon as a bag is opened, the quality of the soil will eventually start to degrade over time. So it is recommended you try to use it before those 2 years are up!
Potting soil has no expiration date and can be used so long as it is not moldy or contaminated. If you’re extremely worried and want to stay on the safe side of things, you can have your soil tested or analyzed.
>> Learn more about this in our article on soil analysis.
Unopened bags of potting soil are typically better in quality and last for much longer periods than bags that have been left open. Bags of potting mix left open and exposed to the elements will have their organic components decompose faster which may promote the presence of insects.
Bags that are sealed and stored in a cool, dry place will last for years on end and will retain their freshness and quality for much longer.
However, if the bag is left open, then not only will the soil be much lower in quality, the more time passes. In other words, there is a higher likelihood that the soil has been negatively altered.
Since it’s been exposed to moisture from the open air, this soil has probably broken down at a much faster rate and may not be as high in quality. Additionally, if it’s left open, this makes it easier for pests to enter.
So if you had to choose between an unopened bag of potting soil and a bag that’s been left open, it is better to go with the former.
In general, there are 3 ways to tell if packaged potting soil is no longer safe to use:
- The soil contains a foul odor
- The soil contains mold
- The soil contains insects
With all of this out of the way, you might still see certain problems arise with older potting soil, especially if it’s been left open. Here are a few signs your potting soil is no longer in good condition.
Potting soil that emits foul odors like rotten eggs may indicate the soil has become anaerobic. To solve this, the soil can be broken down and fed organic matter to help increase oxygen. It could also be left out in the sun for sterilization.
The most obvious sign that potting soil may have gone bad is when it smells bad. Good potting soil should give off hints of slightly sweet earth. This is a sign that the soil is healthy and fertile.
Most times, if your soil smells foul, similar to rotten eggs, this might be an indication that the soil has become anaerobic. When soil becomes anaerobic, this means that oxygen is no longer present inside it and it now contains harmful bacteria, which is why it smells.
Just like us, plants need oxygen to live. If they are grown in anaerobic soil they’ll only have great difficulty breathing due to the lack of oxygen, and may not live long.
If you’ve found a bag of potting soil that smells terrible but still hope to save it, you can help break this soil down with extra nutrients and leave it out in direct sunlight.
Mold is not harmful if seen in potting soil in small amounts. But it is an indicator that the soil has been left in excessively damp environments, and may suggest the presence of pests or a more severe presence of mold growth.
Seeing hairy patches of white or even yellow mold in your potting soil can be startling. While the mold itself is harmless in small amounts, this may be a sign the potting soil was somehow left wet for a long enough time to grow mold.
An opened bag of potting soil that was constantly wet, is another cause for concern.
Such conditions could lead to pest infestation. It also increases the likelihood that the soil has actively decomposed and is now lower in quality compared to soil that’s been left dry.
If you fear that your potting soil is contaminated and plan to use this to sow seeds or plant food crops, I highly recommend that you remove the mold and sterilize the soil.
Again, mold isn’t necessarily bad. But larger mold colonies may become an issue for plants, especially for younger ones.
Potting soil infested with insects, like fungus gnats, is no longer good in quality. This can be harmful to plants and potentially kill them and other plants in the long run. Sterilization is recommended but can be a tedious process.
When you check your soil, the first sign of life you want to see is probably in that of a plant, not unknown insect.
If you check your potting soil only to find it teeming with pests like fungus gnats, this is a good sign the soil is no longer in the best condition.
It’s easy for unsealed bags to be invaded by pests. However, this can sometimes occur even if you think the bag has been closed.
There are some brands of potting mix that come in bags with minuscule holes located near the top. Oftentimes, these small entrances are all that the pests may need to enter the bag and breed inside it.
It can be disheartening to see entire bags of soil infested. If you still wish to use this, you can definitely try sterilizing it. But keep in mind that this will probably be a long and tedious process, and using infested soils like this may do more harm to your plants than good.
Old potting soil can be replenished with the addition of fresh compost and organic matter. However, this must be done with caution. If the soil is already confirmed to contain a high amount of compost, going over the balance of 30% compost in a potting mix may lead to plant burning.
Assuming your soil is still relatively fair quality and completely free of pests and disease, you can rejuvenate this old earth before putting it to use.
Mixing in fresh organic matter and compost can help replenish the nutrients the soil has lost and broken down over time.
How much you use is up to you and depends on what type of potting soil you have. But if you know for a fact your potting soil is already rich and contains a large amount of organic matter, take caution.
Using more than the ideal ratio of 30% compost can potentially lead to your plants being burned.
In this case, you may choose to instead break up and help aerate the potting soil before using it as-is, or only add very small amounts of new compost to prevent harming your plants.
To store potting soil, it must first be fully dried. It should be stored inside resealable, waterproof bags or airtight containers. If kept well in cool, dry places, potting soil can last for several years and be used whenever.
Your potting soil isn’t useless once it hits a certain time, but it certainly won’t be as good as the day it was freshly made and packed or even purchased. Keeping your leftover potting soil in good storage can help the substrate stay fresher for longer periods.
You can open them up and allow the soil to fully dry under the sun. You want to try to avoid excess moisture as much as you possibly can, you may even stir the soil at frequent intervals as well if you wish. Afterward, this can be transferred to a covered, airtight container or a resealable bag.
Inspect the bags to make sure there are no holes or rips for unwanted moisture or pests to enter. I know some people who like to seal their bags with duct tape, but this makes it harder to actually open and close properly.
If there are any rips, you can follow the same steps as above.
Potting soil should always be stored in a dry and cool place free from direct sun, insects, and excess moisture.
If stored properly, potting soils can last for years and years. I know of a gardener who used potting soil over 20 years old, and was still able to grow healthy plants with it!
The 4 different ways old potting soil can be reused are:
- Adding it to compost piles
- Adding it to worm bins
- Reusing it for outdoor landscaping
- Reusing it for gardening beds
If you worry that the soil is too old for you to use, or has ultimately passed its prime, then don’t worry! You can still get some use out of it. Here are some of the ways that you can use old soil.
Decomposed potting soil can be a lovely addition to a compost pile and may help result in a more balanced blend of ingredients.
However, if you suspect this soil has been infected with disease or invaded by pests, this should not be used at all. Using infested soils and debris will only contaminate your compost, and may harm any other plant you use this on, so be sure the potting soil is still clean.
Old and stale soil may not sound the greatest to you, but those worms will love it.
This will make great, organic bedding for worms, especially if there is any decomposed peat moss in it. Make sure the soil is slightly dampened and be sure to fluff it up first, as hardened and compacted soil will not be as beneficial for these creatures.
I have many connections with those working in outdoor landscaping, and they all agree that re-using old and decayed soil is helpful for their work.
Although the soil is no longer as rich, it can still be used to help mix in with their fresher plots of soil and act as an extender. Save your old soil for landscaping projects outside.
Just like using it to extend your materials in landscaping, you can re-use old potting soil similarly to help create new garden beds.
This is helpful when you don’t want to buy large amounts of new potting mix, which can become expensive over time. For the deepest layers inside a garden bed, you can use your old soil to help load up the empty spaces you might have struggled trying to fill.
Infested or rancid potting soil that has already been used for planting can be salvaged through sterilization. It is also recommended to sanitize all tools and pots that have touched the rotten soil. Seeds in bad soil can be treated with hot water, while rooted plants must be transferred.
If you’ve already used up your potting soil only to realize afterward that it may now be in particularly bad condition, this might not be an easy process for you to go through. But you can still take action!
When the seeds you’ve just planted have not yet sprouted, you can still rescue them by quickly removing them and giving them the hot-water treatment.
This will help clean the seeds of any potential pathogens before you plant them in a different soil once more. If these plants have already taken root, this can be harder to handle.
You can try to transfer the plant into a different pot with fresher and safer soil. However, keep in mind that some plants do not transfer very well—they may even die in the process!
So whatever you do, be sure to sanitize whatever pots and tools came in contact with the bad soil to prevent any harmful contaminants from spreading.
Are there plants that enjoy old potting soil?
There are plants that prefer older potting soil. Most plants prefer rich and healthy soil to grow in, but there are some carnivorous or insect-eating plants, such as the bladderwort, that actually prefer nutrient-poor soils!
Can bad potting soil kill plants?
Potting soil that is old and lacking nutrients won’t necessarily kill plants. But if the soil has gone bad and contains mold, foul odors, and insects, then it could potentially kill whatever plants are growing inside it.
Potting soil does not expire. However, it is best used within 1-2 years upon opening, as the quality of the soil will naturally degrade over time.
If kept in optimum storage, soil can be used for years at a time. Poor storage, however, will greatly affect the rate at which potting soil decays, and may lead to infestations or fungal growth.