Does Potting Soil Go Bad?

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    Spoiler Alert: Yes, Potting Soil Can Go Bad

    Potting soil and/or potting mix isn’t very exciting. However, choosing the correct soil or growing medium, especially for indoor plants, is one of the most important steps you can make as a marijuana grower.

    Potting soil can and will expire if it is not stored correctly or used within a reasonable period of time. This article’s goal is to prevent your expensive potting soil mix from going bad, prematurely, give you an overview of why potting soil is essential and much more. Read on to find out more about this important topic.

    Is Potting Soil Even Needed For Container Plants?

    You might wonder if you can just skip expensive potting soil altogether and just use, garden soil, for your plants. The answer to that question is yes, you can. But, you definitely should not.

    DIY Potting soil-You can try to make your own soil mix. However, it is messy, smelly, and, especially for newbie growers, not recommended.

    Why is Potting Mix Mandatory?

    The reason is that unwanted weed seeds, pathogens, and microbes are likely to be present in plain garden soil. So, to start off on the right food, you need to purchase a soil mix that is designed for the potted plant.

    Potting Soil vs. Potting Mix

    Is There A Difference?

    Surprisingly, at least for me, it was, there is a bit of confusion on whether or not potting soil and potting mix are the same. Some websites state that they are essentially the same and many websites use these terms interchangeably.

    On the other hand, other sites state that a potting mix is different from potting soil with the main difference being that that potting mix doesn’t contain any soil, and potting soil may or may not contain garden soil.

    Specifically, potting soil and potting mix are different in the following ways:

    Potting Soil

    • May or may not contain soil and/or sand
    • It is not sterile, which means that it can contain harmful fungi, microbes, diseases, etc.
    • Organic matter i.e. minerals, worm castings, compost, etc.
    • Heavy

    Potting Mix

    • Does not contain soil
    • Designed to not contain any disease-causing pathogens.
    • Depending on the source it can contain both organic and inorganic components.
    • Can contain slow or extended-release fertilizer
    • Lightweight and fluffy, which makes is beneficial for moving plants that are in containers

    Potting Soil Mix Ingredients

    Potting soil ingredients vary by manufacturer. However, most potting soil will have some or all of the following:

    • Sphagnum Peat Moss-This is the main ingredient for commercially made potting soil and is included to enhance water retention.
    • Pine Bark Chips-This ingredient is often used as a safe filer and if it is ground up sufficiently it can, like peat moss, help with water retention.
    • Perlite-It is a natural mineral that originated from volcanic gasses. Is valued for the following: lightweight, ease of use, durability, and water retention
    • Coconut Coir (AKA Coco Coir)– Coco Coir comes from shredded coconut shells and is used to help with water drainage, and soil absorbency.
    • Vermiculite– Is a natural mineral that is related to mica that helps boost plant rooting and moisture control.
    • Fertilizer- Some potting soils/mixes contain timed-release fertilizer. (Most cannabis growers do not recommend that extended-release fertilizers be used)

    Does Potting Soil Go Bad?

    As stated earlier, the straight answer to this question is yes. stored potting soil can go bad, over time, or if it is not properly stored. A general rule of thumb is that the longer it is in storage, the more likely it will be to degrade. The reason for this is that certain soil mix ingredients have a short expiration period.

    For example, one source (house plants and not cannabis) states that peat moss will expire from one to two years. However, Cannabis Business Times though stated that peat moss has a shelf life only from six months to a year. (The same article states that coco coir only lasts from three to nine months)

    Please note, those above product expiration times are severely lessened if the soil comes in contact with moisture, or extreme weather.

    Potting Soil Mix Storage

    Potting soil may have a shelf life. You can though maximize this shelf life by properly storing it. Below are a few tips:

    Storage Container-The best storage container for unused potting soil is its own bag and placed inside an air-tight, rubber tote, like the one shown below. You place used potting soil in that same type of tote and you just have to remember to securely close up the used soil bag.

    Rubbermaid Roughneck️ Storage Totes 3 Gal Pack of 6 Rugged, Reusable, Set of Storage Containers

    Environment-Sun, rain, snow, and humidity can all have negative effects on potting soil. So, keep your old potting soil in a dry area away from the sun.

    What Happens If You Use Expired Potting Soil?

    Using expired or depleted potting soil will likely result in stunted plant growth. It can also cause some of these other problems:

    • Poor Soil Drainage-
    • Added Salt To Growing Medium-
    • Reduce Oxygen Absorption-
    • Plant Disease, Pets Infestation, etc.

    How Can Tell If Potting Soil Is Bad?

    Most of the time, using expired potting soil mix will not be fatal. However, if any of the above happens, you should not attempt to use it or fix it.

    • Bad Smell– If the potting soil bag smells like sulfur or rotten eggs it is likely not useable. (Happens when soil comes in contact with a high humidity environment or water)
    • Pest Infestation-An expired potting mix can be an attractive home for various pests. One pest that is common is the fungus gnat, which is a very small, flying insect that lays its egg in soil. A fungus gnat infestation if left unchecked results in damaged plant roots.
    • Mold– Excess humidity can cause moldy potting soil. And mold can cause a number of problems to your plant.

    All of the above signs are rather obvious and common sense. For example, non-gardeners will be able to smell rancid, soil and also see small insects flying over the soil.

    The thing to remember is that two of these problems (bad smell, and mold) are caused by excess moisture. Excess moisture can be easily fixed by storing your mix in air-tight containers and in proper temperatures.

    Is Miracle Gro Potting Mix Sufficient For Cannabis?

    Miracle-Gro Indoor Potting Mix 6 qt., Grows beautiful Houseplants, 2-Pack

    Specialized potting and soil mix, like Happy Frog, can be quite expensive. i.e. Happy Frog can cost $20 or more per bag than Miracle Gro Potting soil.

    Fox Farm Happy Frog Organic Potting Soil Mix Indoor Outdoor Garden Plants, 51.4 Quart(2 cu ft) ( Bundled with Pearsons Protective Gloves)

    Twenty dollars, for most people, isn’t that much if you are only growing a few plants. But, it can add up if you are growing commercially. So, is the Miracle Gro Potting soil recommended for growing cannabis?

    Miracle Gro Potting Soil MiX

    This is their most popular product. It comes in one, two, eight, and 16-quart containers. It is also quite cheap, has thousands of reviews, and is highly rated.


    Miracle gro has the same ingredients as most other, popular potting mixes. It also has an artificial chemical, extended-release fertilizer (Ammonium Nitrate, Ammonium, and Calcium Phosphates, and Potassium Sulfate) Miracle Grow claims that their fertilizer will last up to six months.

    Is Miracle Gro Good For Growing Weed?

    Miracle Gro is cheap, has thousands of ratings, and has a nearly perfect five-star rating. So, it must work well for your indoor home grow operation? Well, unfortunately, that answer, at least according to reputable sources, is no.

    Three top cannabis-growing websites (Way of Leaf, Grow Weed Easy, and Dude Grows) all tell you to stay away from Miracle Gro.

    Per those sites, the reason you should stay away from Miracle Grow (Or any fertilizer that uses extended-release) is that this product has one nutrient formula that does not change through a plant’s life cycle.

    As you know already, cannabis has several growth cycle stages. (Seedling, Vegetative, Flower, etc) Each of these stages requires different nutrition requirements. Miracle Gro does not give your plants those requirements as it is a one size fits all product. As a result, your plants won’t get enough nutrients (or too many nutrients) if you use Miracle Gro.

    Final Thoughts

    Choosing the proper growing medium, for indoor gardening, is the most important decision that you will make. For example, if you don’t have enough or too much light you can always add or reduce the number of grow lights. But, if you pick the wrong soil, it may be too late for you to fix the problem. And If it can be fixed, it will be a paint to do so.

    That’s why choosing the correct potting soil mix is a make or break it moment. So, choose the best potting mix that you can afford and be sure to store it correctly, and you’ll be on your way to growing dank buds that you can be proud to smoke.


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