How Long Does Miracle Gro Potting Soil Last?


Miracle Gro potting soil is a fantastic fertilizer for plants, and it comes highly recommended due to the copious amounts of nutrients it contains. This fertilized soil is excellent for new plants or beginner gardeners who don’t have their compost going yet. But how long does it last?

Miracle Gro potting soil lasts 3-8 years when stored properly and kept safe from moisture and pests. However, opened Miracle Gro potting soil can be reused so long as new nutrients are reintroduced to the soil via compost or a new bag of potting soil.

In the remainder of this article, I’ll discuss what Miracle Gro is, if you can reuse it, and how to tell if your potting soil has gone bad. I’ll also go over how to refresh the old stuff, plus the drawbacks of using Miracle Gro. So, if you’d like to learn more about using Miracle Gro, be sure to read on. 

Does Potting Soil Expire?

You may never have thought to check your bag of fertilized soil for an expiration date. You probably think it’s just dirt, and how bad can it get? However, the answer might surprise you. 

Potting soil does expire. Most potting soils like Miracle Gro have a shelf life of about 3-8 years before the nutrients in these products are rendered useless. However, potting soil can be revitalized by adding compost or new potting soil to the mix. 

As with most organic things, potting soil can expire, though not how you would think. It doesn’t necessarily rot, curdle, or grow a funny color. That being said, it can still go bad rendering the old potting soil virtually useless to your plants. Not to mention it can even harm them! 

What Is Miracle Gro?

First, you must understand what Miracle Gro is and why it’s so widely used in gardening. 

Miracle Gro is a potting soil blend containing slow-release nutrients necessary for optimal plant growth. This potting soil is great for a range of plants, including vegetables, trees, houseplants, and shrubs, and it contains all the necessary nutrients plants need.

Miracle Gro Potting Soil contains ingredients like:

All of these ingredients contain much-needed nutrients to grow healthy plants. Raspberry bushes specifically benefit from the much-needed nutrients found in Miracle Gro since this soil can help increase berry production.

The nutrients that can be found in Miracle Gro potting soil Include:

  • Ammonium nitrate 
  • Calcium phosphates
  • Potassium sulfate

These three nutrients are vital to most plants’ growth, and they’re perfectly balanced to promote optimal plant growth. However, Miracle Gro only contains so many nutrients and will need to be refreshed with new potting soil or compost over time to continue to work for your plants. 

Can You Reuse Miracle Gro Potting Soil?

Now that you understand that potting soil actually can expire, it’s time to talk about how long Miracle Gro will remain functional. As I briefly discussed, organic matter does expire, and soil is no exception.

You can reuse Miracle Gro potting soil. However, Miracle Gro potting soil will lose its potency over time and need to be refreshed to remain functional. You should refresh your potting soil after each growing season by adding new potting soil or compost to your dirt. 

So as you can see, you can undoubtedly reuse your potting soil. You’ll simply need to add to it to reinfuse it with much-needed vitamins and minerals. I’ll go over exactly how to add nutrients back into your potting soil, but first, I want to talk about how to tell if your soil has gone bad. 

How To Tell Your Potting Soil Has Gone Bad

As with most things that spoil, there are several signs that your potting soil has expired. However, these signs can be challenging to pick up on if you haven’t handled the soil. 

So, let’s go over some of the signs that your potting soil has gone bad:

  • Your potting soil smells funny. An odd odor or rotting smell is a significant indicator that your potting soil is no longer suitable. Too much moisture or fungus can create this smell and render your soil unusable. If your soil appears rotten, you should throw it out or place it somewhere without plants to hopefully dry it out. 
  • Your potting soil has mold on it. If you notice fuzzy tufts of mold, this is a sign the soil is bad and has somehow come into contact with too much moisture. Mold spores can be tough to kill, so it’s probably best to throw the bag out and acquire a new one. 
  • Your potting soil has a lot of bugs in it. Bugs are a significant indicator that your potting soil has turned. If the potting soil appears overrun with bugs, it’s probably no longer usable and should be tossed. 
  • Your potting soil is over three years old. Many ingredients in most potting soils go bad around the 2-3 year mark, which is why most potting soils don’t last longer than eight years. 

If you’ve noticed any of these signs when examining an old bag of potting soil, there’s a good chance it’s no longer suitable. You can dispose of this soil by pouring it out somewhere it won’t harm your plants or simply throwing it away.

How To Refresh Old Potting Soil

Luckily, so long as your old potting soil is free of mold and bugs, there are several ways to revitalize the mix. Let’s take a moment to learn a little about properly refreshing old potting soil like Miracle Gro. 

You’ll need the following materials:

  • A garden hose.
  • A pitchfork or shovel
  • New potting soil.

Here’s the steps on how to revitalize your old potting soil:

  1. Add water. To refresh your old potting soil, it’ll need to be moistened first. This will help you mix in the new soil more efficiently and better activate the nutrients. 
  2. Turn over the old soil. Once moist, you should use a shovel or pitchfork to turn over the soil and break up any clumps of dirt. You should also use this time to remove any old roots. 
  3. Add in some new soil. How much you add will be dependent on the space available. If you want to use the entire bag of new potting soil, that’s also fine. More nutrients are always great. 
  4. Mix the new soil into the old. Use your tool to thoroughly mix the old and new soil together. This will ensure an even distribution of nutrients throughout the old soil and help your plants grow better. 

It’s relatively easy to reintroduce nutrients back into the soil. You can also do this process with your own homemade compost or other types of potting soil. 

If you’re more of a visual learner, I recommend watching CaliKim29 Garden & Home DIY’s YouTube video on refreshing old potting soil. She does a great job of walking you through the simple process:

The Pros and Cons of Using Miracle Gro Potting Soil

Last but not least, I want to go over a few of the benefits and the drawbacks of using Miracle Gro potting soil. Of course, as with any gardening product on the market, there will be pros and cons, so it’s essential that you understand what those are to make an educated decision for your garden. 

Miracle Gro Pros:

  • Provides plant food for up to 6 months.
  • Aids in plant growth.
  • Helps plants bloom more.
  • Can be used inside and outside.
  • Has good drainage. 

All of these benefits are pretty awesome, and these are the main reasons Miracle Gro is so popular when it comes to fertilizing your plants

Miracle Gro Cons:

  • Has high levels of salt, which can result in lawn burn.
  • Utilizes synthetic nitrogen, which can harm soil microbes and worms. 

While there are a few drawbacks to this potting soil, it can be pretty beneficial in small amounts. And, if you’re planting in gardening beds, you shouldn’t have to worry too much about the worms. 

Conclusion 

Miracle Grow has a shelf life of about 3-8 years, but if appropriately stored where bugs and water won’t have access to it, you can always refresh the soil and use it again later. 

However, Miracle Gro’s nutrients tend to get used up within 6 months of use, and additional soil will need to be added to it for optimal plant growth.

If you wonder why potting soil is so expensive, you can read my other article here: 5 Reasons Why Potting Soil Is So Expensive

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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