Does Potting Soil Go Bad?
So the plant flourishes, it should be provided with all the necessary nutrients for growth. When it comes to container-grown plants, proper potting soil plays a key role in their survival. But, does it have to be fresh?
Ever happened to you to leave a container filled with a potting mix from the last season? Or to find an unopened bag in the garage that’s been there for ages? If that’s the case, you must be wondering whether it’s safe to use now for your container garden. Well, actually, the real question here is – Does potting soil go bad?
Let’s find out if you’ll need to spend money on a new one, once again.
How Long Does the Potting Soil Last?
The potting soil doesn’t actually have an expiration date. But still, whether used or not, if it’s not stored properly, it’ll start decomposing over time and lose quality.
To keep the potting blend in good condition, you should store it in a lidded container, protected from any heat sources and humidity. Also, never expose it to direct sun and rain to inhibit microbial growth in the soil.
Therefore, even if it’s already been used over and over, you can use it once again. However, there are things you should take into consideration before putting a new plant into an old potting mix. We’ll discuss them later in this article.
The Composition of Potting Soil
As a matter of fact, potting soil doesn’t contain actual soil. It’s rather a mix of:
- Peat moss – It’s a dead fibrous material which is low in nutrients since it has an acidic pH. It doesn’t compact easily, doesn’t contain harmful microorganisms, it’s well-draining and well-aerated, and releases moisture to the roots as needed.
- Vermiculite – It’s a mined mineral, used to increase the porosity, as well as water-holding capacity of the potting mix.
- Coir fiber – It’s similar to peat moss, yet it’s less acidic, with almost a neutral pH that is. Also, it lasts longer and has higher water retention.
- Sand – It improves drainage and adds weight to the potting blend.
- Perlite – It’s a volcanic rock, which improves aeration and drainage in the potting mix, and modifies the soil substructure. It has a neutral pH.
- Compost – It contains many beneficial microbes and improves drainage of the potting soil, so the plants access the moisture easier.
But, why is it so?
The secret to gardening success is a good potting mix. A good potting mix provides the plant with everything the actual soil doesn’t, a perfect balance of air, nutrition, and moisture that is.
When you grow plants in a container, you’re creating an artificial growing environment. In this case, regular garden soil won’t provide the container-grown plants with enough air, water, or nutrients. Additionally, roots need space to spread, but the room in the container is limited. On the other hand, the garden soil compacts quite soon, preventing the root growth. Therefore, the potting soil beats the regular garden soil when it comes to container gardening.
The good thing is, it’s a man-made creation, which means you can make it, as well as choose the ingredients, all by yourself.
Can You Reuse Potting Soil From Your Containers?
When you do a bit of indoor gardening, one of the most common questions you ask yourself is whether you can reuse the potting soil from your containers. Well, it depends on the condition of the old soil, whether it’s still good or not, and what you’re planting.
What Are You Planting?
First things first, you should never mix different types of plants in the same soil. For instance, if it was some type of flower that’s been planted before, the only right way to reuse that soil is to plant another flower.
On the other hand, if you replace it with some herb, for example, it’s very likely that the new plant won’t succeed. The flower had changed the structure of the nutrients, which will damage the herb once you put it in there.
In What Condition Is the Soil?
Once you’re getting rid of an old plant and putting a new one into the same soil, you should determine whether the soil is still healthy and ready for the next one.
For instance, if the previously potted plant has died, it might have affected the quality of the potting soil. And now, there’s a chance that the very same potting mix you’re reusing will affect the growth of the new plant. To be more specific, here are the risks you should be aware of when using the same potting blend over and over.
The Risks of Soil Recycling
Reusing old soil can put the new plants at risk, because:
- Used soil can contain pathogens – that is, viruses, bacteria, fungi, or other disease-carrying organisms, which can contaminate the new plant.
- Used soil can have a mineral deficiency, because of which the new plant will most likely die.
Any strange odor or a fuzzy layer on the top indicates soil contamination. When that’s the case, start with a new, fresh potting mix.
Reducing the Risks
To make sure your plant will grow healthy in the reused soil, try the following strategies:
- Don’t reuse soil in which diseased plant has grown.
Even when the diseased plant is gone, the soil will still be contaminated.
- Fertilize the soil after planting.
After replacing the old plant with a new one, enrich the soil with some nutrients. Its essential minerals have probably been taken up by the previous plant. Your outdoor soil fertilizer won’t do the job here.
- Refresh the used soil with a new potting mix.
When the soil has been used for a longer period of time, it loses quality. Therefore, to improve the old one, create a 50-50 mix of both used and the new soil.
- Reduce salt with rainwater.
Water the plant with rainwater or melted snow. Since they’re very low in salt, it’s an effective way to prevent salt buildup.
So, does potting soil expire? As long as it’s stored properly, and doesn’t have a sour odor, disease or insect problem, the potting mix can last for seasons.
Does Potting Soil Go Bad? FAQs
The plants absorb everything that’s in the soil, from moisture to nutrients. That’s why it’s important to keep it in good condition and fertilize it as needed. Therefore, even old, the potting soil doesn’t need to be changed annually, but rather every two or three years.
When potting soil is rich in organic matter, there’s a great possibility that your plant will suffer from fungus gnat infestation sooner or later. Since they live in the top of the soil, freezing the potting mix is a very efficient way to get rid of the gnats. Of course, take out the plant first.
You can mix potting soil with garden soil for some cases like raised beds, for example. When it comes to container-grown plants, it’s not a good idea. In this case, you should use a potting mix only. Compared to the garden soil, it’s more lightweight and provides the plant with all the necessary substances. On the other hand, the garden soil contains topsoil, which makes it heavy, dense, and not very rich in nutrients. But it’ll do a great job in raised beds and in-ground gardens.