Does potting soil go bad: 4 signs to watch out for

does potting soil go bad
Opened bags of new potting soil can retain their quality for 6 to 12 months. When potting soil is unopened and unused, it can be stored for about a year or two before it begins to degrade. Potting soil generally lasts longer if stored in a dry and cool environment.

Does potting soil go bad?

Over time, potting soil degrades and eventually becomes unusable. The shelf life of a bag of potting soil is expected to last approximately 6 months when opened. Unless you store it properly, that number may decrease considerably.

A bag of potting soil that has not been opened can be kept in good condition for 1 to 2 years. Even though your bag of garden soil does not have an actual expiration date, the organic material in the soil mix degrades over time.

Moisture content and nutrient levels also decrease over time, so for optimal plant growth, it is best to use good potting soil that is fresh potting soil.

How to tell if potting soil is bad?

If your potting soil is bad, look for these telltale signs:

  1. Getting compacted: the term compaction refers to heavy, tightly packed soil
  2. Foul odors: bad potting soil bags smell like rotten eggs
  3. Insects
  4. Mold: moldy soil means it’s bad

1. Compaction

Compaction refers to soil that is dense or tightly packed. It is a common problem in old soils or mixes containing peat moss.

Peat moss is only viable for 1-2 years, so when it decomposes with other organic matter, the soil becomes dense.

2. Foul Odor

If your potting soil bag smells like rotten eggs, it is likely that it has gone bad.

A foul smell is caused by anaerobic bacteria that thrive in old, damp, and compacted soil. 

3. Insects

Insects, such as fungus gnats, indicate that the soil is unsuitable for planting. As fungus gnats feed on decomposing organic matter in the soil, they deplete nutrients and damage the roots of plants.

Therefore, the soil will not be suitable for the growth of plants. 

4. Mold

There is a problem with your soil if it has mold growing on it. It usually occurs when moist soil is stored in closed bags for an extended period of time, especially during warm weather.  

It is recommended not to use this expired potting mix since it may cause root rot in container plants.

Can You use old potting soil?

Yes, you can reuse old potting soil. Used potting soil from indoor plants, outdoor plants, or houseplants is generally acceptable as long as whatever you were growing in it was a healthy plant or tree. 

If you observe pests or diseases on your potted plants, it would be best to sterilize the mix to avoid infecting the plants next year.

How to sterilize old potting soil?

The first step is to remove the old plant, any plant roots, grubs, leaves, and other debris from the old potting soil.

After that, determine the best method for eliminating microbes and insects.

1. Solarizing

  • This method involves placing old potting soil in lidded, five-gallon buckets or black plastic bags tightly tied shut and allowing them to dry in the sun for four to six weeks. 
  • The buckets or bags are heated just enough to kill any bugs or pathogens that are present.

2. Oven

  • In an oven-safe pan, cover it with foil, and bake it for 30 minutes at 180 to 200 degrees Fahrenheit.
  • You should also use a candy or meat thermometer to ensure that the soil temperature does not exceed 200 degrees. Toxins can be released at higher temperatures.
  • After the soil has been baked, take it out of the oven and cover it until it has cooled.

3. Microwave

  • Place moistened old potting soil in microwavable containers of quart size.
  • Use microwavable lids – do not use foil – that can be poked with ventilation holes or can be cracked to allow steam to escape.
  • For every two pounds of soil, heat at full power for approximately 90 seconds.
  • Before using the soil, remove the containers, cover the vent holes with tape, and allow it to cool completely.

So, Is dried out potting soil still good?

It is still possible to use dried-out potting soil. If the soil contains sufficient nutrients, it can be rehydrated and used for growing plants.

  • Rehydrate dried-out soil by placing it in a shallow tray of water.
  • The soil may take a couple of hours to absorb the water.
  • You could always mix your dried-out soil into your compost pile and then repurpose the soil.

Remember, whether container gardening or planting in the ground, use mulch to keep your soil moist.

How long is unopened potting soil good for?

It is possible to store unopened bags and unused potting soil for about a year or two before it goes bad.

Potting soil generally lasts longer when stored in a cool, dry environment.

How to store potting soil

You should store potting soil in its original bag, inside a protective container such as a storage tote. 

Sterilite clear tubs and Rubbermaid totes are good options and repurposed containers.


Discovering composting as a way of life or even better, as nature’s way of recycling, Ana dedicates her time to trying out new methods of composting at home. Her goal is to share everything that she’s learned in the hopes that it will help others discover the amazing rewards of composting.

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