Does potting soil go bad? Explained

Well, potting soil is a crucial component of your raised beds and container garden. It doesn’t matter if you’re gardening outdoors or indoors, excellent quality potting soil is essential to make sure your plants receive the best possible growing environment. 

Most often than not, you may be glaring at the leftover or used potting soil and wondering whether or not it will go bad. You may have some doubts, like whether you need to replace it with fresh soil or if you can go ahead and use the old potting soil mix anyway. 

One question that keeps popping into your mind would probably be, “Does potting soil go bad?”

bad potting soil

Table of Contents

Does potting so go bad?

Potting soil can go bad due to the decomposition of its organic ingredients, such as peat moss, which can occur over time if it has not been stored properly. This can lead to a loss of the soil’s ability to retain water and provide adequate aeration for plant roots, which can be detrimental to potted plants. Therefore, it is important to store potting soil in a suitable environment and use it within a reasonable timeframe to ensure the soil remains healthy and effective for plant growth.

reuse potting soil

What are the main ingredients in potting soil?

In general, potting soil happens to be a “soil-free” growing medium, because it’s not just soil like your usual garden soil. Potting soil, typically, consists of the following ingredients: perlite, vermiculite, slow-release fertiliser, peat moss, coconut coir, and pine bark.

Each of the above-mentioned ingredients seems to have a specific function to help plants thrive:

  • Perlite is the small, Styrofoam-ball-like stuff in the potting mix. While it doesn’t hold water, it keeps the mix aerated and lightweight. It also helps the roots develop and thrive.
  • Vermiculite helps with aeration as well. Moreover, it can hold water and enhance soil moisture levels.
  • Slow-release fertiliser provides your plants with a sufficient amount of nutrients to effectively last the growing season.
  • Peat moss and coconut coir hold water.
  • Pine bark, which breaks down slowly, helps provide good drainage.
perlite is not organic material

How do you identify good potting soil?

The following characteristics distinguish good potting soil:

  • The best potting soil is lightweight in nature. It has a low density and helps with soil aeration.

  • It drains water easily. It holds just enough water to accommodate the needs of the plant.

  • It is nutrient-rich, containing essential nutrients like phosphorus and nitrogen.

  • Good potting soil is loaded with beneficial soil microbes that increase the availability of nutrients for plants.

bagged potting soil

How to tell if potting soil is bad

A majority of potting soils are composed of peat moss and various other organic ingredients that actually decompose over time. As a result, the soil loses its water retention and aeration capacities, making it unfavourable for any potted plant.

The four signs that your potting soil has gone bad and has to be amended or replaced include bad odour, pest and insect infestation, mould growth, and a dense texture.

  • New potting soil smells moldy: An unpleasant smell is one of the first signs to look for to check if your potting soil has gone bad. A rotten egg smell emanating from your potting soil is a surefire sign that it has gone bad. This odour is caused by fungi and bacteria that are actually decomposing the organic matter present in the soil.

  • Pest and insect infestation: If you notice pests and insects in the potting soil, you can be sure that it is spoiled. The decaying organic matter in the soil attracts bugs and other pests. Insects like fungus gnats can also be found. While these are harmless to humans, they can eat your plants’ roots and destroy them completely.

  • Mould growth: The presence of mould is another sure sign that the potting soil has become bad. Mould generally grows on the soil surface and is grey, white, green, or yellow in colour. it often has a slimy texture or can appear fuzzy. Mould normally forms when the potting soil is moist or has remained wet for a long time.

  • Dense texture: If your potting soil has started to form clumps, you can be sure that the soil has gone bad. This generally happens when the peat moss starts to decompose. As the soil runs out of organic matter, it tends to compact and the texture becomes denser over time. As this happens, there will be drainage problems and it becomes difficult for roots to thrive.

Aside from these four signs, checking the expiration date is a must. It gives you a rough idea of how long you’ve had the potting soil and when you should discard it. However, the expiration date is actually not the end of it. If you see that the soil doesn’t show any signs of having gone bad despite its expiration date, it is fine to use it.

moldy potting soil

How should you revive old potting soil?

As mentioned earlier, merely because your potting soil has become older, it doesn’t mean you’ve got to dispose of it. The good news is that there are still a few ways in which you can repurpose the old potting soil.

  • Composting: One way to reuse old potting soil is by adding it to the compost pile. The process of composting is a great option to recycle your old soil and provide your plants with some of the nutrients they require. Besides, the compost pile will help keep the soil in your garden healthy.

  • Vermicompost: Using worm casting is another method to add nutrients and enhance your soil quality. Worm castings or vermicompost are a kind of organic fertiliser made from the waste of earthworms. Vermicompost is available in a gardening store, but you can make it at home using your old potting soil. You can do this by simply placing a layer of your old potting soil at the bottom of a container or bin, and then adding earthworms. As the earthworms tend to eat their way through the soil, their waste will easily enrich the soil with several nutrients. In a few months, this potting soil will turn into rich, black vermicompost that you can liberally use to fertilise your plants.

old potting mix

How do you store potting soil?

In general, bags in which potting soil is stored are sealed tight, but if you want to extend the storing period for a few more months, place it in a plastic bin and then close it firmly.

A few potting soil bags tend to be resealable, allowing you to open them when needed, take as much soil as you require, and reseal them. If you notice that the bag isn’t resealable, you can seal the bag using duct tape and then keep it in an airtight container. Remember to place the container in a dry and well-ventilated place. 

How long does potting soil last

Once the bags of new potting soil are opened, you can expect the soil to retain its quality for about 6 to 12 months. If the soil bag is unopened and unused, it is possible to store it for almost a year or two. Generally, potting soil tends to last longer when it is stored in a cool, dry container. 

unopened potting soil

Conclusion

In conclusion, potting soil can lose its quality over time due to the decomposition of its organic ingredients, leading to a reduction in its ability to retain water and provide adequate aeration for plant roots. To prevent this, it is crucial to store potting soil in a suitable environment and use it within a reasonable timeframe. By taking these measures, you can ensure that your potting soil remains healthy and effective for plant growth, helping your plants thrive and flourish.

potting soil conclusion

People Also Ask

Should potting soil be sterilised?

In fact, there are chances for even fresh potting soil kept in unopened bags to contain pathogens. So, to be on the safe side, it’s recommended that you first sterilise the potting soil before potting cuttings and seedlings or sowing seeds. The best way to sterilise the moist potting soil is to microwave it and kill all of the pathogens and pests in it.

Does potting soil go bad upon freezing?

Well, freezing your potting soil doesn’t make it turn bad. Perhaps it could be a great way to sterilise the soil. If your potting soil is contaminated with tiny pests, fungus spores, or pathogens, freezing the bag for a few days can kill these pesky pathogens. When you are about to use it, give the frozen potting soil some time to thaw, and mix it with the required organic materials.

Should you replace potting soil each year?

The rule of thumb with regard to potted plants is to freshen up your potting soil once a year. However, you can make it once every two years if you see that the plants are growing pretty slowly and the soil is not depleted. To freshen up the potting soil, you should add slow-release organic materials, mix it well so that it drains well, and stir the soil to oxygenate it.

Can I use the potting soil again?

Of course, yes, if the potting soil is not contaminated with bacteria. Besides, this depends on how long the soil has been in the containers or pots.

If the soil is relatively fresh after just a few months of use, you can certainly reuse it, but if it has been in the plant container for over a year, I recommend that you fill the container with fresh soil.

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Oliver Wright
Oliver Wright

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