Sometimes I buy more potting soil than I need because there’s a discount on them. But I found that there’s a limit on how long the potting soil can remain in its best condition.

Potting soil will last for 1 year in a sealed bag and 6 months in an open bag. This depends on how and where you store it. You want to place it in an airtight container and store it in a cool, dry place like a basement.

I’ve written some more details below that will help you understand better how long your potting soil can last. So keep reading.

Opened bag

An opened bag of potting soil will last you 6 months if all the conditions are ideal.

I would suggest using the potting soil as soon as you have opened the bag. This ensures it will work the best for your container plants giving them the right moisture, texture, and nutrients.

If you have leftover potting soil, you can keep it in the same bag if it’s resealable and thick enough that it won’t tear in storage.

I would recommend resealing the bag and storing it in an airtight container till you are ready to use it again. This method will help keep the potting soil good for 6 months.

Unopened bag

An unopened bag of potting soil will last you 1 year if all the conditions are kept ideal.

If you have an unopened bag of potting soil, it’s best to keep it sealed. Store it in an airtight container and place it in a cool, dry place till you can reuse it.

This potting soil can remain fresh for about a year after you have sealed and stored it.

How to make potting soil in a bag last longer

There are ways you can make the potting soil last longer depending on how you maintain the soil.

Maintain the organic materials in the potting soil

You just need to keep adding the materials that will keep on degrading in the stored potting soil.

The most common ingredients that will deteriorate fast are organic ones. This includes materials like peat moss, organic matter, and organic fertilizer.

I suggest that every 2-3 months you keep adding a little of these materials to keep the potting soil fresh. You can add peat moss, organic compost, and organic fertilizer.

Maintain the texture of the potting soil

The texture of the potting soil will degrade as materials like peat moss start to deteriorate. The material in the potting soil will become finer.

This texture will not allow moisture and air to circulate well through the potting soil. The best thing to do is add a little perlite and organic compost every 2-3 months to the potting soil.

Maintain the nutrients in the potting soil

The potting soil that you have bought may or may not contain a slow-release fertilizer. You want to ensure that the potting soil is dry before you store it.

Otherwise, the slow-release fertilizer will be activated due to the moisture and it will not be available when you use the potting soil later.

I also recommend adding some slow-release fertilizer and compost to the potting soil every 2-3 months when kept in storage.

How to tell if the potting soil in the bag has gone bad

You should store the potting soil in a sealed bag and container that is kept in a cool, dry place. But if the soil was already in a moist environment, chances are it may have gone bad.

Bad smell

If you opened the bag of potting soil and there is a bad smell, it means the potting soil cannot be used as-is.

Since the soil was having moisture and it was in a closed bag, the anaerobic bacteria would have started acting on the soil. That’s why you get a bad smell as a result.

You can get the soil back to normal conditions just by spreading it out on a tarp in a sunny location. The air, light, and heat will get rid of the unwanted bacteria and smell. You’ll need to keep this soil on the tarp for 1-2 weeks to get it back to a good state.

Pests

The potting soil may be infected with pests if you have kept it in a damp, dark place. The most common pest is the fungus gnat that can get inside the bag through a small hole.

The fungus gnat will lay their eggs in the potting soil that will hatch and feed on the organic material. The gnats are not harmful to the soil or mature plants. But they will destroy any seedlings you try to start in such potting soil.

You can place the potting soil on a tarp in a location that gets good air, heat, and sunlight. And in a few days, the gnats should have got out of the soil. You can also use a fungicide if you want to get rid of the fungus gnats faster.

Mold

If the potting soil is left in a cold, dark, and damp place, mold will start growing on it. When you open the bag, you’ll see white spots on the potting soil which could be Mycelium.

It’s easy to get rid of mold from the potting soil by exposing it to heat and light. So put the potting soil on a tarp and place it in a location that gets good sunlight. Keep this tarp out for 2-3 days and the mold will disappear from the soil.

How to reuse the potting soil left in the bag for a long time

You may have bought more potting soil than you need. Maybe it was available for a discount. And now you have a lot of potting soil bags in your basement sitting there for several years.

The good thing is that potting soil does not expire. Only the organic components do. And the texture of the soil changes. This means you can put such potting soil to reuse with a little work.

Revitalize as potting soil

If you want to you can make the potting soil usable once again for plants. But you will need to add the missing organic materials back again.

The easiest way to do this would be to use 50% new potting soil mixed in with 50% of this old potting soil from the bag. This will help save costs when you’re buying new potting soil.

The other way is to mix in the missing organic materials by using organic compost and slow-release fertilizer.

Add to your compost pile

If you just want to dispose of the old soil, it’s good to add to your compost pile. The potting soil will provide the right base.

Use as filler material

If you’re growing plants in large containers, you may need to use some filler material at the bottom. This filler material will help you save costs as you don’t need to use new potting soil.

You can reuse the old potting soil as such filler material at the base of the container. This old potting soil has a texture that is compact and does not allow fresh potting soil to go through easily. That’s an ideal condition for filler material.

Cover holes in the yard

You can use the old potting soil to cover up holes that any animals may have created in your yard. This could be from animals like rabbits, moles, voles, or rats.