Does Potting Soil Go Bad?

Have you ever pondered this question, ‘Does Potting Soil Go Bad?’

It totally makes sense! Potting soil is loaded with organic matter, some are enhanced with fertilizers, manures, beneficial microbes and more. So, does it go bad?  What if you see little mushrooms popping up? Gnats in the bag? Mold?

Check out our "Does Potting Soil Go Bad" video for the lowdown!

Does potting soil expire?

This is a yes and no kind of answer! If you are willing to do a bit of work and rejuvenate your potting soil, then the answer is no, not really. If you simply want to assume that your soil will always be perfect the moment you open the bag and, forever and ever, then yes, the quality of it will decrease!

Yes, we have seen it all!  What to do, what to do? Here’s the dirt on potting soil!

What Is In Most Potting Soil?

Potting soil is a blend of organic and inorganic ingredients that creates a nutrient rich medium to grow vegetables, fruits, flowers, herbs, houseplants, and more, generally in pots and containers, and for seed starting. Most potting soil is a mix of peat moss, coconut coir, vermiculite, perlite, bark, compost, fertilizers, other organic matter, including manures, and even worm castings. This blend of ingredients is intended to maintain proper moisture levels, and should be well-draining, providing room for roots to grow, breathe and uptake nutrients.  Your potting soil should ultimately support your plants so they can grow their best and thrive.

What is not in potting soil? Soil! Yes, there is no soil in potting soil. Why? Good old fashion soil may carry pathogens, and other not so friendly organisms that can infect plants and seedlings. Not the best way to start out a gardening experience.

What Is The Difference Between Potting Soil and Garden Soil?

Have you seen bags of garden soil at your garden center? Garden soil is totally different from potting soil. If you are looking for the perfect soil for your houseplants, seed starting, potted plants and smaller container garden, do NOT grab that bag of garden soil. Why? This is actually soil! Yes, garden soil is topsoil that may be enriched with compost, fertilizers, organic matter and more. Take a peek at the ingredients so you know what you are buying. It is common to see things like bio-solids, which is matter recovered from a sewage treatment plant, chemical fertilizers, and other ingredients that you do not want! So, why use garden soil?  It is great for larger areas, to build up soil in your planting beds, to add structure to existing soil and you can even use it in raised beds. It is generally much cheaper, and affordable, thus a great option for when you need a lot of it.  Here is the tricky part…garden soil may carry pathogens, weed seeds, diseases, fungus, and more.  If you are dealing with tender, young plants, and houseplants, manufactured garden soil can be a risky option.

Check out our Compressed Potting Soil post for the lowdown on one of the best potting soil options!

How To Tell If Potting Soil Is Bad?

So, can potting soil go bad even if it comes sterilized, free of fungus, pathogens and diseases? Does potting soil expire? Just like that moment when you open a fresh bag of baby spinach for dinner one night, your bag of potting soil that was once sterile and sealed, is now exposed to oxygen, light and moisture, and now it begins to change.  Unlike that baby spinach, your potting soil will not go bad overnight or in a few days, but yes, it can begin to turn and it starts to lose the benefits that it once had.

Signs That Your Potting Soil Is Bad

Smell: If you notice an offensive smell, similar to rotten eggs or spoiled food, it is possible that the organic matter in your potting soil has been exposed to moisture and has begun to decay.  Add in the potting soil’s natural bacteria population being exposed to moisture and oxygen, and your soil is now hosting and breeding things that are creating a not so friendly smell.  Simply pour your potting soil out onto a tarp or cookie sheet, and allow it to sit in the sun for a few days. The sun will break down any unwanted bacteria.  Once treated, store it in a well sealed moisture proof container or bag.

Insects and Pests: Little pests like gnats, fruit flies, ants and even larvae and eggs, love to make themselves at home in open potting soil bags.  It is the perfect dark, damp place to start off their babies, but not optimal for us gardeners. You can dump your infested potting soil out onto a tarp, cookie sheet, or anything that makes it easy to clean up, and spray it with a treatment of neem oil.  Follow the manufacturer's instructions for neem application, treat it, let it sit out in the sun, and then treat it once more in a few days.  Once your potting soil is dry, go ahead and store it in a well sealed insect proof container or bag. If your potted plants are attracting pests, it could be due to overwatering and water standing in the catch dish beneath your plant.  Soggy soil is the perfect breeding ground for pests like gnats.  Pay attention to how much you are watering and eliminate any standing water.

 

Mold and Mushrooms: White fuzzy mold and cute little mushrooms happen when there is enough moisture for an extended period of time.  It is natural, but it can be hazardous to young plants and seedlings, and may ultimately cause root damage in established plants.  Once again, sunlight can treat this issue, and then store your soil in a moisture proof container.  If you are seeing mold in your potted plants, it is best to remove the soil, check your plants for root rot, repot with new potting soil and make sure that you are not overwatering your plants.  Got mushrooms popping up in your plants?  Mushrooms spread by spores, which love to travel by air.  Those little spores are stored underneath the mushroom cap; carefully remove the mushroom caps, with a tissue, trying your best to not spread the spores everywhere. . Mushrooms are more common in gardening soil due to ingredients being sourced from mushroom farms, manures, etc. If the problem gets out of hand, repotting is key!

Compacted: If the surface of your potted plants looks cracked and dried out, your potting soil has become compacted, and maybe even ‘hydrophobic’.  I love fun words like that.  Hydrophobic means that it does not absorb water, but rather it repels.  This is obvious when you water your plants and the water runs straight through.  That is never a good thing in gardening, it means that your plants are most likely not getting the hydration they need.  The best way to address this is to repot your plants.  You can reuse the soil, please don’t toss it, simply enhance it with a high quality coconut coir, known for retaining water and moisture, and reinforce it with some organic plant food, then repot your plant babies and carry on.  If this is an issue with your outdoor plants, slow watering by setting a hose in the pot and letting it trickle to avoid compacting your soil.  Large amounts of water flooding the soil makes it impossible for plant roots and the soil to absorb, and it creates a ‘crust’ on the soil surface.  Slow watering gives the roots time to absorb the water, and it helps maintain a healthy soil structure.

Plants Not Responding Well: Plants come in the most minimal sized pots with soil that has been most likely fed a few times over its lifetime.  Remember, plants in pots rely on us to feed them and care for them.  Once the potting soil is completely depleted of nutrients, your plant is waiting for you to feed it!  If you see your plants yellowing, looking less vibrant, not producing as much, dropping leaves, getting sick, and not growing their best, then it may be wise to consider the health of your plant’s soil.  This is by far the easiest to solve, feed your soil and plants! Yes, give your plants and soil exactly what they need, food!  Get in the habit of using a high quality organic plant food every 2-4 weeks or a long lasting granular plant food once a month.  Just like us, they need good food to thrive!  Do not let your plants starve!

How To Store Potting Soil

Is there a way to store potting soil so it doesn’t spoil? Yes there is! One of the biggest contributors to potting soil issues is moisture and light. So, the best way to store it is in a clean, airtight, sealed container that doesn’t allow light, moisture and oxygen to get in there and liven things up.  Without those three elements, there is a decreased chance of mushrooms, mold, fungus, fruit flies, and other pests making themselves at home. Stash your air tight potting soil container in a cool, dark place, like in your garage, potting shed, or basement, if possible.

If you are repurposing old potting soil, it is best to treat it by allowing it to sit out in the sun for a few days, remove any old plant matter, to avoid spreading unwanted diseases and pests, and then place your treated potting soil in its own clean, airtight container.  You want to ensure that your treated potting soil stays free of unwanted visitors too!

How Long Does Potting Soil Last?

Potting soil is the perfect soil medium for starting seeds, transplanting houseplants, container gardening and more, but just like any soil, the nutrients break down and ultimately the soil will become just ‘dirt’! Most potting soil comes fortified with organic matter, plant food, manures, essential plant nutrients, beneficial microorganisms and more, and time does degrade the nutrient density of these additions.

After 6-12 months, the nutrient levels in bagged potting soil has begun to steadily decline.  This doesn’t mean that it is spoiled or expired. It simply means that it isn’t as nutrient dense as it was when it was manufactured.  Plus, if potting soil isn’t stored properly in an airtight container or bag, the exposure to oxygen, light and moisture will speed up this process. 

Can I Use Old or Used Potting Soil?

After 6-12 months most bags of potting soil have lost some, if not most of their nutritional value, but they are still safe to use.  It just won’t have optimal food to feed your plants. Most potting soil can be stored 1-2 years without spoiling if stored properly, but its nutrients will still degrade. So, yes, of course you can use old potting soil, but it will not provide the same results that new, nutrient dense potting soil will.

What about used potting soil? Yes, you can reuse old potting, but keep in mind that it will need a bit of input to rejuvenate it and ensure that it is free of pathogens, pests and unwanted visitors. Tossing used potting soil is a waste of organic resources!  With a few easy steps, your old and used potting soil can be as good as new, if not better!

Does Unopened Potting Soil Go Bad?

Yes and no!  It doesn’t ‘go bad’ or ‘spoil’ and it generally isn’t harmful to your plants.  However, most soil manufacturers do state that their potting soil mixes may not be as effective, and nutrient levels and efficacy may be reduced after 2 years from date of manufacture. This is especially true for potting soil that has been enhanced with beneficial microbes.

What should you do if you find a bag of ‘expired’ potting soil?  Easy!  Go ahead and open it up, revive it with a quality organic plant food that is high in essential nutrients and beneficial microorganisms, and continue to feed your plants and soil every 2 weeks during the growing season.  You may be surprised by how long you can actually use soil time and time again, and by the fact that you should never toss soil, unless it is infected with disease and pests beyond repair.

How To Revive Old or Used Potting Soil

With this being said, if you have old bags of soil, do not toss them out, rejuvenate old or used potting soil with a high quality organic fertilizer, even mix in a few handfuls of compost, and it will come back to life. Before adding in fertilizer, it is wise to heat treat used potting soil by sitting it out in the sun for a few days.  Spread your used potting soil on cookie sheets, perfect for small amounts, or on a tarp, and let the sunlight and uv rays work its magic.  Now your soil is almost as good as new.

I love mixing one tablespoon of Organic Plant Magic Soluble Plant Food powder to one gallon of old or used soil to reboot depleted soil before planting.  Not only does it add in every essential plant nutrient but it is loaded with beneficial microorganisms, humic acid, kelp and more. When your soil is alive, your plants will show it! Yes, your soil should be ALIVE!

Get in the habit of feeding your plants and soil at least once a month. Potted plants and soil rely on us to rejuvenate and feed them. Without frequent additions of organic matter and food, soil becomes depleted and ineffectual. If your goal is to grow amazing things, then you need to stay on schedule and feed your plants and soil regularly!

Conclusion

Not all soil is the same, and of course things do expire, go bad, or simply grow old, but with some knowledge and a bit of effort, you can ensure that you got it all under control.  Isn’t that true for every plant part of the plant and gardening experience?  Never stop digging, you don’t know what you may learn!

“Now you know. And knowing is half the battle.”