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Does Potting Soil Go Bad? [3 Ways to Tell for Sure!]

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While we go to great lengths to nurture our garden and vegetable plots, neglecting the soil in our indoor and container-grown plants is too easy. While you can reuse it under the right conditions, potting soil has an expiration date, and if you don’t use it promptly and maintain it, your plants could suffer.

Potting soil goes bad over time, and you need to rejuvenate it regularly if you want your plants to stay healthy and happy. All soil loses aeration and nutrients over time, which are critical for plant growth.

So – here is one of the most popular questions gardeners ask us: does potting soil go bad? We’ll answer this question in depth in this article and help you understand how long your potting mixes and soil will last. We’ll also teach you how to recognize when it’s expired and how you can reuse and rejuvenate it. 

Does Potting Soil Go Bad? Or Can You Save It for Next Year?

Potting soil goes bad if your plants extract all of the nutrients or if the organic materials in the soil all break down. New potting mix generally stays in decent shape longer because plants and microorganisms break down things like peat moss more rapidly.

While potting mix can go bad, there are a few more variables to consider. The truth is that soil is a complex blend of organic and inorganic materials. It also contains a thriving mixture of microorganisms that keep the soil and plants healthy.

Like any system, the soil needs constant maintenance to keep it in good shape. In the natural world, soil maintenance happens through many complex processes, where new organic matter is continuously incorporated to become part of the soil.

For example, garden worms, fallen leaves, and organic compost help replenish natural soil.

However, many chains in this system are broken regarding our potted plants, especially when we keep them as indoor plants. Your potted plants get cut off – and isolated!

How Long Do Potting Soil Nutrients Last?

sage and marjoram mixed herbs in pots
Does potting soil go bad? Over time, yes! Some potting soil doesn’t contain many nutrients and needs frequent amendments. Other potting soils contain slow-release fertilizer. That way – your potting feeds your plants slowly over time. Our favorite potting soil mixes contain fertilizer prills. Prills are tiny capsules (with resin casing) of fertilizer that release slowly.

Potting soil nutrients generally last for one to two years when there’s a plant growing in it. However, some plants are greedy feeders and will need more fertilizer. Other slow-growing plants may not use up the nutrients quite so quickly.

Store your soil in a (chilled) dark location in storage containers for the best results. If you leave your soil bag open in a hot and humid place, it will degrade much faster.

Is It Okay to Use Old Potting Soil?

It is okay to use or reuse old potting soil in most cases, but if you want your plants to thrive, you’ll need to ensure that it is nutrient-dense. In addition, some plants fare better in poor conditions, and old soil can be perfect in this situation.

An excellent example is woody perennial herbs, such as thyme, rosemary, lavender, and oregano.

These plants will not thank you for a container of nutrient-rich compost and prefer more natural (and unideal) soil conditions. Some old soil mixed with horticultural sand will be perfect for keeping your Mediterranean herbs happy and thriving.

What Happens If You Use Old Potting Soil?

young lime tree in pot with fresh soil
Soil isn’t just dirt! Good potting soil contains a mixture of soil, peat moss, coir, and vermiculture. Some soil also contains humus, bark, and other organic compounds. Potting soil also contains perlite. Perlite is perfect for increasing the aeration of the soil. Kind of like garden worms!

If you use old potting soil for your plants in containers, you may find that your plants do not grow as vigorously as you had hoped. For vigorous growth to occur, your plants will need the ideal light level, temperature, water, and the correct type of fertilizer.

The latter two come from the soil, and low-quality soil will leave your plants malnourished and thirsty. When soil is fresh and new, it contains precisely the right balance of components to keep your plants happy.

An ideal balance of soil nutrients will include something to add structure to the soil, such as peat moss, which can keep the moisture level just about right. Also, a high proportion of organic matter provides essential nutrients.

Over time, this delicate balance changes, and the potting compost will no longer be enough for your plants to thrive.

So, whether you are trying to decide whether your plants need repotting, emptying old containers, or have found an old bag of compost in the shed, let’s find out how to tell if your soil has spoiled.

Read More – How to Build an Apple Tree Guild!

3 Ways to Tell If Your Potting Soil Is Bad

compacted clay dirt
Compacted soil is too lumpy and dense for air, water, and roots to move throughout. When using potting soil, always break up lumps as you find them to keep the soil from suffocating your plant’s roots.

Do you suspect your potting mix is spoiled or depleted? These are the dead giveaways:

  • The Potting Soil Gets Dense and Compacted
  • The Potting Soil Smells Bad
  • Your Plants Are Not Growing

We go into much further detail regarding these soil snafus – and how to solve each problem below.

We hope these help you grow happier and healthier plants!

1. It Is Dense and Compacted

Compact soil is a common problem in potted plants, where the planting media within the container become too dense and firm.

In the natural world, insects and microorganisms constantly move and aerate the soil. However, this process cannot happen in your containers, and as water passes through the soil, it will become denser and harder.

If you cannot push a finger effortlessly into the top inch of your soil, it has become compacted and unhealthy. Compacted soil is a common problem when using compost that contains peat moss, as this breaks down and becomes compacted over time.

How To Fix Dense and Compacted Soil

To fix compacted, dense soil, you will need to add more air and drainage. To do so, you can poke at the soil with a bamboo skewer or remove it from the container to break it up. 

Your compacted soil needs the chance to expand! Break it free from the confines of the pot and gently loosen any large, firm lumps.

To add some structure to your soil, mix in a generous helping of coconut coir or any other aeration-providing organic ingredient. 

To prevent soil compaction in the future, you can also bottom water your container plants. Bottom watering ensures that the water will not press down your soil. 

2. The Potting Soil Has a Bad Smell

healthy tomato plants growing inside
Always seek fluffy and soft potting soil. And – carefully read the label of any potting soil you buy! Not all organic soil is okay for potted plants. If you choose the wrong potting soil – your potting soil may get too heavy and compact! Potted soil compaction makes it difficult for your plants to breathe – and grow. Not ideal for growing plants!

Potting soil that smells bad has most likely become waterlogged. The complex ecosystem in soil needs air and water. Too much water means harmful bacteria will thrive, and the good bacteria will all die.

Potting soil that has a foul smell may also be a sign of root rot or mold. In these cases, the soil has already likely become compacted, creating anaerobic conditions.

In these oxygen-free soils, you’ll notice an unpleasant smell, a damp environment, and possibly, mold growth. When this happens, your plant’s roots are begging for oxygen. 

How to Fix Smelly Potting Soil

To fix smelly potting soil, empty it from the pot onto a tarp (tarpaulin) or concrete slab in direct sunlight. This process will remove excess moisture content from the soil and discourage fungal and anaerobic bacteria growth.

You can use this soil again, but you will need to add some aeration and drainage.

Smelly soil likely does not contain much organic matter and microorganisms. A good remedy is to mix it with some soil improver, well-rotted compost, or manure.

3. Poor Plant Growth

wilting potted plant
If your plant has stunted growth or starts wilting suddenly, your potting soil might be missing some nutrients or have become compacted.

There are many reasons why some plants fail to thrive, but soil quality is often a key culprit. If your plants are in perfect environmental conditions but look stunted and poor, the nutrients in the soil have likely become depleted. 

Remember that the soil in pots does not have the same opportunities to regenerate as the soil in the ground. The plant will soon take all the available nutrients, and eventually, there will be nothing left for the plant to eat.

In cases such as these, soil additives come in handy to keep your soil healthy.

How to Fix Depleted Potting Soil

Potting soil depletion is a situation where prevention is vital. You can keep your potting soil in good health by mimicking the natural cycle of soil health. However, there are still some ways to reuse your old potting soil, even if it becomes depleted.

Add a top dressing of nutrient-rich worm castings or compost every few months to feed the soil. You can lightly mix this with the top inch or two of soil. The insects and microorganisms will do the rest.

You may use artificial fertilizers as a quick fix to boost the health of your plants, but they will do nothing to replenish your depleted soil. You’ll need compost to make it healthy for your plants. 

If you think the mix in your container is past the point of rejuvenation, you will need to empty the container and replace it with fresh potting soil.

However, don’t discard the old soil! There are some tricks to bring it back to life.

How Do You Rejuvenate Old Potting Soil?

worms on garden shovel with soil
When we plant things in containers, we remove the plant from the rest of the ecosystem. So, to grow a plant in a pot, we need to manually do all the work that the worms, animals, and microbes in our ecosystem do for wild plants.

Now for the fun part – magical soil rejuvenation! 

You can rejuvenate and reuse old potting soil by incorporating soil additives to bring back the structure, aeration, and nutrients. An aerator like coconut coir and fertilizers like compost and worm castings can replenish it. 

If your soil is old, has poor drainage, or is low in nutrient levels, there are several things you can do to rejuvenate it. 

Add Structure, Aeration, and Drainage

Firstly, you will need to add structure to the soil to provide adequate drainage. Coconut coir is perfect for bringing your potting soil back to life. And it is a more sustainable and longer-lasting option than peat moss.

Other options include compost, bark chips, and perlite.

Fertilize the Soil

Secondly, your old potting soil needs a boost of nutrients. While you could use artificial slow-release fertilizer granules, why not use organic fertilizer?

Worm castings contain high concentrations of organic matter and nutrients, which mix easily with old potting soil.

You can find worm castings at a range of outlets. However, if you want them for free, setting up a vermicompost worm farm will give you a constant supply of liquid fertilizer and worm castings. If you want to learn more about worm farming, you might find our other article on the Best Worm Farm Kits and Composters helpful.

You can also mix in a bit of homemade compost material to help enrich your soil and add beneficial microbes back into it. 

Read More – How To Improve Garden Soil Naturally [Over Winter and Year-Round]

Can You Reuse Potting Soil From a Dead Plant?

You can reuse potting soil from a dead plant, but only if the plant did not die of infections like root rot or white mold. In addition, the soil will (probably) benefit from some rejuvenation.

Rejuvenating your soil means re-adding fertilizer and some bulk to reach the proper conditions.

Still, before you can reuse the potting soil, you should remove any roots or plant leftovers from it. We also advise breaking up large clumps of lumpy soil to improve aeration and drainage.

Even if you think the soil is beyond repair, we advise against throwing it away or chucking it in the trash! Sprinkle it on top of your compost pile or vegetable beds, and the worms, insects, and microorganisms will soon incorporate it back into the ground.

The only case in which you should not use old potting soil is if there is harmful bacteria or mold growth in it.

For example, if the soil has a rotten smell, it may have become infected. In these cases, it’s usually best to retire or sterilize it to prevent possible infestations. 

Potting Soil Going Bad? Read Our FAQs!

Choosing the right planting medium for your plants can be tricky, so we’ve put together a comprehensive guide to how long your potting soil can last and how you can use and reuse it!

How Long Can You Use Potting Soil?

You can use and reuse potting soil as long as it is still nutritionally dense. In most cases, fresh bags of potting soil will go bad within six months if you do not add anything to keep the beneficial microbes alive and preserve the aeration. 

Once you open a bag of fresh soil, the compost will begin deteriorating in quality due to moisture loss. So, it is best to use potting soil within six months of opening the bag.

Your potting soil will stay fresher for longer if stored correctly. Air and moisture loss will cause the unused soil to deteriorate, so reseal the bag or empty the contents into an airtight bin.
It is also critical to avoid waterlogging or excessive dampness. Overly wet potting soil, even in the bag, can become a breeding ground for fungi like white mold. 

Does Potting Soil Go Bad After a Year?

Potting soil may go bad after a year, depending on how you store it. After a year, unopened potting soil will have degraded in quality, but it is not necessarily unusable.

In other words – your potting soil is not necessarily bad. It won’t harm your plants. Still, it may not provide enough nutrition to keep them happy for a long time.

Read More – 11 Herbs With White Flowers So Pretty, You’ll Want to Pluck Them!

Conclusion

We love growing many potted plants, from tomatoes, zucchini, and jalapeno peppers, to herbs and flowers. We love them all!

Still, we also know that all potted soil eventually goes bad.

We hope our guide helps shed light on how to rejuvenate potted soil – even if it depletes entirely.

If you have more questions about how to feed your potted plants, feel free to ask!

Thanks again for reading.

Have a great day!

More Reading On Gardening and Soil Improvements:

Does Potting Soil Go Bad? 3 Ways To Tell And How To Fix It

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