Does potting soil go bad and expire? How long does it last?

Potting soil does not go bad if stored and used properly but its organic matter and nutrients break down over time making it less fertile.

When it’s potting time, you may buy some bags of potting soil and not use all of them at once. Sometimes you have some of the used potting soil sitting around and you don’t know if it is still good to use. But does potting soil go bad?

Potting soil does not go bad if stored and used properly but its organic matter and nutrients break down over time making it less fertile. Some potting mixes have an expiry date but you can still use them even when old by adding them to your compost instead of throwing them away.

Does potting soil go bad

Potting soil does not go bad for a long time when stored properly. The ingredients and components of potting mix do not expire and will be usable for a long time. However, the quality will continue to degrade when unused over a long time and you’ll notice a change in nutrient levels, texture, and moisture content.

Does potting soil go bad

You can store potting soil for even one year without it expiring. Keep in mind that the quality of the organic matter in your potting soil is important for the healthy growth of plants. The longer it stays without being used, microorganisms continue to break down the organic matter in the potting mix, making it less nutritious for potting plants.

Moisture loss is also another problem with old potting soil. When it stays for long, the moisture content drops, leaving the mix to dry up. You’ll either end up with a thin texture.

It is also possible to end up with compacted potting soil if a lot of moisture content forces it to compact into dense matter. So, if potting soil mix does not go bad, how long can it last? After how long will it still be useful?

How long does potting soil last

Unused potting soil can last about 6 months if stored properly before losing its quality or going bad. To increase its shelf life, store potting mix sealed in its original packaging and put it in a protective container such as a storage tote. This will make the soil last longer than when exposed to the environment.

Storing your potting soil and mix in a climate-controlled place is the best option to make it last long. Too much heat or extremely low temperatures can affect the quality of the soil, making it go bad eventually.

Does used potting soil expire?

Used potting soil will not go bad and can be used for 1 to 2 years before all the nutrients and qualities degrade and make it useless. Do not throw the soil away. If you used your soil last season, you can still put it to use in the new season with great success.

However, it is important to know that if the old potting soil mix contained peat moss, it will expire after 1 to 2 years and will not be usable afterward. It will no longer have any rooting benefits for your houseplants.

Pro tip: Even used potting soil can be used again if it is rejuvenated properly. All you need to do is jump start the soil to get it back in good condition. This will probably save you money because you won’t need to buy new potting soil every season.

Signs your potting soil has gone bad

Although it is a good idea to reuse potting soil and potting mix, you have to be careful not to pot your plant in damaged soil. Soil that is damaged or infested can mean the plant does not grow healthy.

Here are signs that your potting soil has gone bad:

It starts to smell bad

Potting soil that has gone bad will start to smell really bad. The rotten smell may resemble that of a rotten egg because anaerobic bacteria that thrive in compacted soil with less oxygen.

You can fix this bad odor by killing the bad bacteria in your potting soil that’s spoiled. Spread the stinking soil on a surface in the sun and allow it time to dry. The sun will kill the bad bacteria that are making your potting soil to stink.

Insects and pests

Another sign your potting soil has gone bad is the presence of little insects crawling all over it. Fungus gnats are the most common because they infest rotting matter.

Fungus gnats may not harm mature plants but can really case root damage to young plants.

It grows mold

Do you see dusty looking mold on potting soil? It could be white, yellow, or green. It is a sign that your potting soil has gone bad. A good solution is to place the soil in a well-ventilated area, preferably in the sun to get rid of the mold.

Do not use potting soil that’s infested with mold because it can cause root rot in your plants. Soggy potting soil is vulnerable and highly likely to grow mold, so you should be careful how you handle it.

If the soil has gone bad to an extent you cannot reuse it, you may want to throw it away. However, if the mold is not too much, you can treat the potting soil with an antifungal remedy to prevent root rot in the plants you’ll use it for.

How to reuse old potting soil

does potting soil go bad and
Photo by agrobacter from istock

Since your potting soil has not gone bad, you may want to put it to use even if it has degraded. I would recommend rejuvenating it to revive its quality before using it.

However, be careful not to pot plants using soil that is infested with pets and diseases such as fungus. You’ll need to inspect the used soil to make sure it has not expired or gone bad to a level where you should just throw it away.

Put it in your compost

Instead of throwing away your potting soil, add it to your compost pit to add volume and organic matter to it. Simply spread it over the compost heap to add to the decomposing matter.

This way, you’ll have recycled your potting soil after it expires. You may notice small particles of perlite even after the compost decomposes, which shouldn’t be something to worry about.

Add to a worm bin

If you’re setting up your worm bin, you may need some materials such as soil and wet newspaper to make the bin healthy and functional. Old potting soil that’s expired or unused will can be useful in this case.

Throw it in your outdoor garden

That soil in your planters may be depleted and the nutrients broken down and used by your indoor plant, but it is not entirely useless. Add it to your outdoor garden when you think the nutrients are depleted.

It will help add volume and more organic matter to your garden soil. Try not to till the garden in order to mix your potting organic matter with the soil. This can disturb everything going on in your garden. With time, the soil will mix with that in your garden.