Did you find an old bag of potting soil while cleaning out your garage or gardening shed? You’re probably wondering if it’s expired or still fine to use! Potting soil is an important aspect when gardening and planting, especially for those who plan on using raised beds or container gardens.
So obviously, you wouldn’t want that potting soil to go to waste, nor do you want to kill growing plants with bad potting soil. But does potting soil go bad, or is this just a gardening myth?
Read on to find out!
The short answer is YES, potting soil does go bad. However, there are things to consider.
About Potting Soil
Potting soil is a type of soil made for plants, confined to a small area, and requires more nutrients and texture for the plants to breathe properly. While potting soil can be used for the outdoors, they aren’t necessary for plants to grow properly since they have an open environment with natural and direct sunlight and drainage.
Potting soils are made of different ingredients to maintain appropriate moisture, texture, and nutrients for plants to grow. One of the major ingredients potting soils have is peat moss.
Peat moss is efficient when holding moistures, also contains a ton of nutrients vital for healthy and proper plant growth. If ever you have an open bag of soil that is peat moss-based sitting in a bag for a few months and it’s gotten wet, then expect that it has decomposed.
That said, it doesn’t mean that this soil isn’t completely unusable, though it won’t be ideal for proper potted plant growth, nor can it sustain life. This soil will be better off used outdoors in larger gardens.
There are other types of potting soil you can use on potted plants, such as premium, professional, plant-specific, or all-purpose.
All-purpose potting soil is the typical choice for average gardeners, a premixed soil when potting new houseplants or repotting older ones requiring larger containers. Premium and professional potting soils might contain ingredients like time-release fertilizer, which feeds plants for a few months for stronger root development, though a bit expensive. There is also plant-specific potting soil used for certain plants such as cacti or succulents that require different sets of nutrients.
Does Potting Soil Go Bad?
Now that we have tackled what potting soil is, do they go bad?
They don’t really have a shelf life, though they can lose nutrient levels, moisture content, and texture over time if they aren’t stored well. It can still be used, but the growing results won’t be what you expect compared to fresh soil.
This is because potting soils have an organic matter that will inevitably break down over time to a dustier consistency, thus becoming denser. This would make it less able for water and nutrients to circulate throughout the pot and plant, gaining access to the roots. It results in less drainage, thus drowning the roots.
Let’s take a look at the ingredients within potting soil:
- Vermiculite is a mineral that does not expire.
- Perlite, like vermiculite, does not expire
- Pine Bark extract, used with other ingredients when making pycnogenol, may expire, but the bark should not.
- Peat Moss can expire, decomposing right away. They are at their best around 1-2 years after purchasing it.
So yes, potting soil does go bad after 2 years if left unopened, and while still usable, it’s not recommended to use it. If it were an opened bag, you should be using it within 6-12 months, as factors like air and excess moisture would reach the soil inside, breaking down nutrients and compressing the soil quicker.
Furthermore, you should consider the area it was stored in. When sitting in a damp environment or areas it can get rained on, the quicker it ends up soiling.
That said, it’s best to use soil within 1-2 years or even shorter than that, as peat moss and other organic materials contained in the potting soil would be actively breaking down even when you leave the bag unopened.
Rarely, there come instances when potting soil will go completely bad, so they should never be used on your plants. You can tell if potting soil has gone completely bad if you notice the following:
- Rotting smell
- Mold growing in your potting soil
- More gnats flying in and/or around your bag
- You see that it is past the expiration date
With all this in mind, there are ways you can make your potting soil last longer, whether they are over 2 years old or if they have stayed unopened:
- Mix more nutrients into your potting soil, such as granulated organic fertilizer or homemade compost. If adding compost, add 1-2 inches to the soil on the top. For those using fertilizer, follow the directions stated on the packaging.
- Compaction would make soil dry, so you may want to try adding a bit of water, which can let the soil particles move apart a bit for better aeration. However, do NOT soak the potting soil in water, which may do more harm than good. Only add water in small amounts.
- Blend the older soil with fresh potting soil, but make sure that you do so in correct quantities. Ideally, you should have one part perlite, one part vermiculite, and four parts peat moss.
- If ever your potting soil is completely useless, you may use it as worm castings or add it to your compost.
Wrapping It Up
Potting soil can indeed go bad, which is why it’s important to use it according to instructions and based on the expiration date. While there are ways to extend its lifespan, it’s best to use it while it’s fresh to ensure that your plants grow healthily.
If you have a bag of potting soil about to expire, do use them properly soon!