Does potting soil go bad? An open bag of potting soil can usually retain quality for 6 to 12 months, but if there are no signs of rotting or dampness, it can likely still be used.
The longevity of your potting soil is affected by the soil type, storage conditions, and what you are hoping to do with it. This guide will detail all of the factors that go into using and storing potting soil for your plants.
What is Potting Soil?
Potting soil is a mixture of organic ingredients designed to create a healthy environment for your potted plants. It’s mixed in such a way as to keep the soil from becoming too compact, allowing for good drainage and root propagation.
The looseness of the soil differentiates the mix for garden soil, which tends to be more compact. You may also hear the term “potting mix.” This is similar but is strictly soilless meaning that it is sterile. These mixes are more expensive.
Types of Potting Soil
The material that makes up your potting soil will make a difference in how quickly it will become unsuitable to use.
- All-purpose: A common general mix suitable for most plants.
- Organic potting mix: Made from organic material only and very fertile.
- Seed starting mix: A very fine mixture allowing roots to grow and expand easily.
- Moisture control potting soil: Moisture pellets are added to prevent the soil from drying out completely.
- Outdoor potting mix: Made to mimic forest soil conditions, and usually have moisture-retaining pellets and extra fertilizer.
The different components of each soil will mean that they break down differently and have different shelf lives. If the plant has extra nutrients or porosity, these factors may be reduced.
If you need the soil to be of specific quality for a specific plant, then sticking to the 6-month expiry is a good idea. For less fussy plants, you can use the soil if you do not see any signs of bad soil (see below), or you can look at other ways to reuse the soil.
Storing Your Potting Soil
Keep open potting soil in a sealed container away from heat and humidity. The best storage container to use is a durable galvanized can. Keep this container out of the rain and direct sunlight.
Signs of Bad Potting Soil
A bad smell, especially one of rotting eggs, is a sign that water, and then bacteria, has entered the soil. You can spread this soil out in the sun to dry it out. This will kill the bacteria and can return the soil to a usable state.
You may go back to your soil only to find pesky insects crawling from it. These are fungus gnats, and are annoying but will not cause harm. Drying out the soil will rid the soil of them.
As fungal spores are common in potting soil, mold can easily develop during storage. Mycelium, a white mold is a result of too much moisture sealed inside a plastic bag.
You can kill off this mold with fresh air and sunlight. Spread out the soil in your garden on a sunny day to do so. However, ensure that the fungus is completely gone before using the soil.
Do not use soil that has had mold for new seedlings as the young seedlings will be unable to compete with the fungus if there is any left in the soil.
Ways to Use Old Potting Soil
If you believe your potting soil may be too old to have the proper nutrients or porosity to allow your plants to grow well, here are some ways to revive it:
Blend with Fresh Soil
Mix new and old soil in a 50-50 mixture to revive older potting soil without leaving the soil lacking in nutrients to grow plants.
Mix in More Nutrients
Adding fresh organic matter such as compost to the soil can add the nutrients to the mix that your plants need.
If you have no use at all for the soil and you believe it won’t be good for your plants to use it. This addition can help keep insects away from your compost and hasten the breakdown of organic material within it.
Does Potting Soil Go Bad – Conclusion
It’s good to live by a ‘waste not, want nor’ mentality, it’s better for the environment and better for your wallet. If you don’t think your soil has gone off, then feel free to use it.
If you think it may not offer enough to your plant anymore, then rejuvenate or compost as per the guide above. Also, check out our guide for the best potting soil for herbs growing in containers.