You found some old potting soil in your garage or shed and wanted to use it on your plants, especially because it was expensive when you bought it so you don’t want it to go to waste. But, you might wonder if it’s still safe for your plants.
Does potting soil expire or go bad? Potting soil does expire. If you’ve opened a bag of potting soil, it will last for about six to 12 months, so you should ideally use it during this time.
If you use expired potting mix on your plants, this can disrupt the salt content of your plant’s soil, not drain the soil properly, or reduce the amount of oxygen your plants require from the soil, so it’s not recommended.
Here’s what you should know about potting soil lifespan.
What Is Potting Soil?
Potting soil is a blend of ingredients that nourish your plants. These ingredients prevent soil compaction so that plant roots get enough nutrients, water, and oxygen they need to thrive.
A potting soil mix is fluffy and lightweight while being able to retain moisture.
Some common ingredients in potting soil include:
- Inorganic materials. These boost drainage, aeration, and moisture retention, and can include sand, pumice, or perlite.
- Fertilizers. These give plants nutrients and include ingredients such as bone meal and kelp meal.
- Organic matter. This includes rice hulls, sphagnum peat moss, manure, compost, and earthworm castings. These help to aerate the soil and make it healthier with essential nutrients plants require.
- Additives. Potting soil can also contain additives that balance soil pH levels and wetting agents to retain more moisture.
How Long Potting Soil Lasts
If you own a bag of potting soil and you’re unsure of its lifespan, check the bag for an expiry date. Generally, if your bag of potting soil is unopened, it can last for about six months before its ingredients will start to degrade.
If the bag has not been opened yet, a bag of potting soil can usually last for around one or two years.
Potting soil contains many ingredients, but not all of them go bad. Let’s explore some common ingredients found in potting soil and how long they last.
- Peat moss. This is an ingredient that helps the soil better retain moisture. However, it’s quite a volatile potting soil ingredient as it starts to decompose very quickly. After being added to potting soil, it will have a lifespan of between one and two years.
- Vermiculite. This ingredient, otherwise known as aluminum-iron magnesium silicates, increases soil aeration and prevents compaction. It doesn’t expire.
- Perlite. This encourages greater soil aeration. It also doesn’t expire.
Signs Your Potting Soil Has Gone Bad
You can tell that your potting soil has gone bad and shouldn’t be used by checking for the following signs:
- The bag of potting soil is wet. If you’ve stored your potting soil bag in an area of your home where it’s been exposed to moisture, you shouldn’t use it. This is because moisture affects the ingredients. For example, peat moss will start to decompose if it’s been exposed to moisture.
- The potting soil smells unpleasant. If you open the bag of potting smell and pick up rotten-egg smells, this is because bacteria have been growing in the compacted soil.
- The potting soil is infested with bugs. If you can see fungus gnats, which are dark, small insects, in the potting soil, this is a sign that the soil is rotting. Fungus gnats are attracted to moisture, so they’re a sign your potting soil has gone bad.
- The potting soil is moldy. If you see mold on the soil that looks dusty and is white, green, or yellow in color, the potting soil is bad. Mold can cause plants to experience root rot, especially since mold is commonly found in wet or humid conditions.
Why You Shouldn’t Use Potting Soil That’s Gone Bad
Using potting soil that’s not fresh can be unhealthy for your plants. This is what it can do and why you shouldn’t use it if its expiration date has been met or it’s showing signs of degrading.
- Potting soil can compact your plants. When potting soil decomposes, it compresses. Its particles become too packed around the roots of the plant, which prevents them from getting enough oxygen from the soil. This starves the roots and can cause plant death.
- Potting soil lacks effective drainage. Since potting soil particles become compacted when they start to decompose, they will prevent water from effectively draining into the soil. This could cause waterlogged plant roots and root rot.
- Potting soil causes excess salts. When the soil can’t drain, this results in fertilizer salts building up in the soil, putting strain on the plants and burning their roots.
- Potting soils that contain fungus gnats can damage roots in young plants.
How To Prolong The Shelf Life Of Potting Soil
You must store your potting soil properly so that you increase its lifespan.
- Keep potting soil in a lidded, airtight container that’s far away from heat sources.
- Keep your potting soil in an area of the home that doesn’t contain high levels of humidity.
- If you’re keeping your potting soil in its original container or bag, secure it and put it in a can or plastic bin to ensure it’s protected from moisture and air.
- Store your potting soil in an area of the home where it’s not exposed to rain or direct sunlight, both of which can promote bacterial growth in the soil.
Can You Reuse Potting Soil?
When repotting plants in containers, you might wonder if you can reuse potting soil. You can, but you have to ensure you follow the correct guidelines.
- You should clean and amend the potting soil after use to ensure it’s still of high quality. Remove any plant debris, such as roots, that are in the soil. You should also run water through it to remove its excess salts.
- Mix the potting soil with fresh compost, sticking to a 1:1 ratio. Add a bit of lime and gypsum, as well as a teaspoon of fertilizer per every gallon of soil.
Important note: You can reuse potting soil if the plants you were growing in the soil were healthy. If they were diseased, you’d have to sterilize your soil.
So, once you’ve followed the above tips, you will then have to remove insects and bacteria from the potting soil. Here are two methods you can try:
- Solarizing. This technique is when you put old potting soil in airtight black plastic bags and then put them in the sun for four to six weeks. The heat that forms inside the bags will kill pathogens and bugs.
- Put it in the oven. You can sterilize soil by putting it in an oven-safe container, or covering it with foil if the container doesn’t have a lid, and baking it at 200 degrees Fahrenheit for half an hour. Just be careful not to heat the soil at a temperature higher than 200 degrees as this can cause it to release toxins.
Other Uses For Expired Potting Soil
If your potting soil has expired, you can still use it in other ways. Here are some to consider so you don’t throw it in the trash.
Use It In Areas Of The Garden Without Flowers
While old potting soil might not have the fresh ingredients to help your plants grow healthy, you can mix old potting soil into the ground in any areas where you don’t have plants.
Or, another idea is to put a thin layer of potting soil on the ground between plants, as long as you keep it away from plant crowns. These are where the stem of the plant comes up from the ground and connects it to the roots.
Use It To Keep Moisture Away From Your House
Another creative way to use old potting soil is to apply it around your house foundation. This can be a useful way to prevent moisture from entering your home, such as if you usually end up with water in your basement.
What’s the difference between potting mix and potting soil?
While potting soil can sometimes contain soil, potting mix doesn’t contain soil. Instead, it contains other ingredients, such as coir, bark, vermiculite, and compost.
Is it safe to use garden soil in pots or containers?
Garden soil isn’t appropriate for indoor potted plants because it doesn’t maintain the correct levels of moisture. This can saturate the plant roots, resulting in root rot.
If you want to use potting soil on your plants to encourage their health and growth, you might wonder if using expired potting soil is safe for use.
In this article, we’ve explored everything you need to know about how to use potting soil that’s expired and when to toss it out.