Does Potting Soil Go Bad? What To Look For Before Using Bagged Potting Soil

hand holding potting soil checking if potting soil has gone bad

Does potting soil go bad?

Yes, potting soil can go bad, but there are many ways you can rejuvenate your old used and unused potting soil, it doesn’t necessarily have to be tossed out.

Potting soil can spoil within the first year of purchase. The main reason for this is that potting soil is composed mostly of peat moss.

Because peat moss is a cheap ingredient, potting soil manufacturers use it in their mixtures. It is convenient and lightweight, but it also decomposes quickly with a lifespan of only about one to two years.

If a fresh bag of potting soil gets damp or soaked in the rain, the peat moss will begin to decompose. The potting soil will no longer be healthy for potted plants.

Heat and direct sunlight will also cause potting soil to break down and lose the essential nourishment plants need.

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How to know if potting soil is bad?

There are 5 ways to know if your potting soil is bad.

  • Smell
  • Condition of bag
  • Insects
  • Shrinkage
  • Mold

Smell: A telltale sign that potting soil has spoiled is if it smells bad. to know if your potting soil is bad is the smell. If your opened or unopened bag of potting soil smells like rotten eggs, it has likely been exposed to a large amount of water. Bad smelling soil is caused from excessive water, resulting in bacteria growth which emits a rotten smell. This is why it’s important that potting soil be stored in a dry area.

Condition of Bag: Before buying a bag of potting soil from your local garden centre, there are a few things you should check for. To determine if unopened potting soil has gone bad, look at the condition of the bag. A wet bag with holes in it was not stored properly. Potting soil should be stored out of sunlight, remain sealed and kept dry. If the bag looks to be in good condition and feels dry, it should still be good for use.

Insects: Fungus gnats are often a good indication that your soil conditions are off. If you’re noticing small flying insects around your plant you may have a fungus gnat problem. These little insects are attracted to the moisture in potting soil. Fungus gnats feed off of the decaying plant material and fungi. Again, another reason why monitoring the moisture level in your plant’s soil is important. Identifying and treating fungus gnat infestations are key to keeping your plant alive.

Shrinkage: To know if the potting soil that is in your pots is bad watch for shrinkage. Potting soil that is in use begins to sag in the pot, making it seem like there is less potting soil than what you started with. As the peat moss decays, the potting soil will sink and can clump around the roots of the plant which could lead to a whole different slew of problems for your plant such as suffocating roots. When potted soil shows clear signs that the peat moss has decayed, it is time to change the soil.

Mold: If your potting soil looks like it has been dusted with white powder, mold is growing on the soil. Sunlight and fresh air will kill off the mold, but it could impact your plants negatively. Instead of scraping the mold off and mixing it with fresh new potting soil to try and rejuvenate it I like to air on the side of caution and toss moldy soil outdoors in the compost area.

If your potting soil is showing any of these signs, it’s time to toss it and start fresh.

Now that we know that yes, potting soil can go bad, let’s take a look at a few other commonly asked questions about potting soil and how to know if it’s time to replace what you have.

Does potting soil expire?

Yes, potting soil that contains peat moss does have an expiry.

Potting soil is made up of a variety of different ingredients. Most of the ingredients used in common mixtures such as vermiculite and perlite do not expire, however peat moss (as mentioned earlier) has a limited lifespan.

Just like a carton of milk or a bag of chips, potting soil has an expiration date stamped on the bag. The expiration date is usually printed on the back or top of the bag. Check for this before buying any potting soil.

Also check for conditions we listed above such as mold, dampness or a rotten smell – if the bag you’re considering using has any of these signs, it’s likely that the soil is expired or bad.

Throw your expired potting soil into your compost and buy a new bag.

How long can you keep potting soil?

Unused potting soil will be at its best for the first six months before it starts to lose its qualities.

To prevent potting soil from becoming damaged or too dangerous to use, the best way to store unused potting soil is to tightly seal the bag it is in and place the bag inside a plastic bin or metal tin where water can’t get into it. Keep the container out of direct sunlight, away from moisture and rain, and away from any sources of heat.

Used potting soil generally lasts for one year and should be refreshed each spring with fresh soil. Plants need loose, aerated soil to grow healthy and stay alive. By replacing the old potting soil, you are ensuring that your plant’s roots can breathe and don’t starve due to lack of nutrients.

Potted soil that looks dusty or has mold growing on it should be replaced immediately to protect the plant and prevent it from dying.

What should I do with old potting soil?

Just because potting soil has been used does not mean that it is worthless. If you have the time and space, you can rejuvenate used soil as long as it does not have mold on it or insects in it.

First, spread out the used potting soil and pick out any debris, such as stones and plant parts. Next, rinse the soil with water to remove the buildup of excess salts. Finally, mix the potting soil at a 1:1 ratio with fresh compost bought from a gardening supply store. Mix in a light dusting of lime and gypsum and add a general fertilizer as per packaging instructions.

Store the rejuvenated potting soil in a container with a lid to keep it dry and out of the sun. Use it within six months.

If rejuvenating potting soil is more work than you have time for, simply toss the old and used potting soil into the garden or the compost pile.

More Plant Care Advice and Helpful Tips

If you’ve checked all these things and realize that your potting soil is still in good shape but notice your plant isn’t doing so well, check out these other plant care articles:

What Is The Best Potting Soil For Houseplants?
7 Reasons Why Houseplant Leaves Turn Yellow (and how to easily fix them)
Do Indoor Plants Need Drainage?