Potting soil is an indispensable part of a gardener’s toolkit. It provides plants with all the essential nutrients and facilitates the passage of water and oxygen through the roots.
In all essence, it is as important to a gardener as is a hammer to a blacksmith.
Commercially, potting soil is usually sold in large packs, making it impossible to use at once. Can you store it for extended periods?
Let us see if potting soil goes bad and how you can prolong its life. But, first, let’s look at what it is made up of.
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What Is Potting Soil Made Up Of?
The primary ingredient of almost all potting soils is peat moss. It is a dark brown and coarse organic material produced by the natural decomposition of sphagnum moss.
It helps hold essential nutrients for absorption through the roots and retains moisture content.
The two other main ingredients are bark and pearlite. While pearlite, a type of volcanic glass, prevents the soil from getting too dense, bark improves aeration and regulates soil temperature.
Can Potting Soil Go Bad Or Expire?
The short answer is yes, potting soil does go bad depending on how you store it. Its primary constituent, peat moss, is organic and can decompose slowly into a dustier form. This leads to an increase in the density of the mix. Dense soil is unfit for growing plants.
Why does A Bad Potting Mix Pose Big Problems?
- Putting your plants in a dense potting medium is essentially putting them in concrete. There is no way water and nutrients can circulate through the mix and be absorbed by the plants, leading to root rot.
- Insufficient drainage leads to salt buildup, stressing the roots further and stunting plant growth.
- Plant roots are deprived of oxygen, leading to the early demise of the plant.
Unused sealed bags of potting soil usually last for more than a year. You can check with the producer for more information.
However, if stored in a cool and dry place, opened bags can last for about six months. The soil in them starts losing its nutrient composition after that.
However, it can still be salvaged by adding nutrients. We will come to that process in a while.
How To Check?
A bad potting soil has specific characteristics that you need to know.
First, check the density or compactness of the soil by touching it with your hands. It should crumble easily.
If it is too dense or compact, you already know why it is useless.
Further, check if it has a bad smell. A foul odor like ammonia is usually an indication of anaerobic decomposition rendering it useless.
Also, check if insects are moving around it. Some insects like fungus gnats will prove detrimental to almost any plant grown in that soil.
What’s worst is that they lay numerous eggs and quickly spread to other plants.
How To Store Potting Soil?
You must keep the unopened bags in a cool and dry place for best results. We suggest storing the remaining soil in clean and washed trash cans for bags that have been opened.
Use duct tape around the lid to seal it off thoroughly.
Ensure that the soil is completely dry before storing it. Drying becomes more critical in winters because soils can become moldy in environments with excess moisture.
Look out for rough white patches on the top surface of the soil. These are white molds.
You can dry the soil in bright sunlight by spreading it out on a tarp before storing it.
Can You Use Old Potting Soil?
Old, compacted, and unused potting soil can be revived by adding suitable materials to alter its composition.
- Take out the insects– If your potting mix is infested by fungus gnats, you need to dry it completely under direct sunlight and let it remain dry for a few days. You can then discard the top 1 or 2-inch layer because it is where the larvae and eggs usually thrive. Alternatively, deploy a sticky yellow trap to attract and remove adult fungus gnats from the soil.
- Sterilize the soil– You must sterilize the old soil before enhancing or using it. Sterilization wipes out any harmful organisms or disease-causing pathogens. The best way to do it is by placing your sealed storage container directly in bright sunlight for 4-6 weeks. The build-up of heat inside the containers takes out the microorganisms.
- Add coconut coir to the mix– Coconut coir is an eco-friendly alternative to peat moss. It improves the absorbency, moisture retention capability, and drainage of the soil and decomposes more slowly than peat moss.
- Boost Nutrient Levels– Adding additional organic matter and nutrients is an excellent idea to boost your old potting mix. However, it also boils down to the plants you intend to grow. Depending on the need, you can use compost, worm castings, or organic fertilizer.
However, if you believe that the old potting mix is useless, you still don’t need to throw it in the dumpster. It can be used in many alternative ways:
- In raised beds and borders
- To fill up holes in your yard
- In compost piles
- As regular outdoor garden soil in place of using in indoor potted plants
The Difference Between Potting Soil And Potting Mix
Although we have used both the terms interchangeably, there is a slight difference between the two.
Potting Soil – It may or may not contain soil. It may contain pathogens as it is not sterilized.
Potting Mix – It is a strictly soilless medium and does not contain any pathogens on being sterile. It is safer to use for indoor plants.
Many variables affect the growth of plants, with the quality of the soil or the potting medium being the most significant one.
Fresh soil is indeed imperative for the healthy growth of your indoor plants. You now know how to determine the quality of your potting soil and enhance it if required.
I have found gardening to be my calling since being restricted to my apartment. I love studying rare species of plants and giving them a mention on my blog. I also love growing organic vegetables in my backyard.