Testing Popular Potting Mixes: Our Surprising Results

Purchasing the right potting mix can be stressful, time-consuming, and expensive. How do you know which brand will actually perform? We decided to take matters into our own hands at the Epic Homestead. Epic Gardening founder Kevin and Garden Hermit Jacques experimented with 14 popular brands of potting soil to find which ones work best for growing high-quality organic vegetables. 

This article explains the experiment and results, plus simple recommendations to help you choose the best potting mix for your garden.

14 Popular Potting Soils: Our Tests & Results

A soil blend isn’t just dirt in a bag. Every brand at the garden or hardware store has its own nuances. To make matters more difficult, there are many confusing marketing terms and labels listed on potting mix bags. If you don’t have hours to read the ingredients of every option (we definitely don’t!), this experiment offers real-world insights into the best picks.

Why We Tested Potting Soils

Bagged potting mixes can cost anywhere from $10 to $100, depending on brand, size, and inputs. From compost to peat moss to perlite, you can find a massive diversity of ingredients in bagged blends. Some of them even have “biosolids” (treated sewage sludge) mixed in! If this sounds gross or unhealthy for your garden, you will definitely want to keep reading to ensure you choose a mix that is organic and high-performing. 

Potting mix selection ultimately comes down to two main questions: 

This experiment uncovers which potting soils are a complete waste of money and which ones are the best for home gardeners.

How We Created the Experiment

We decided to create an experiment to figure out which popular potting blends actually enhance plant performance. This backyard experiment is not a valid scientific result. However, it is a real field trial with actual garden plants and real-life variables. Unlike lab experiments, this test includes all the nuances of real-world gardening, like varying sunlight, temperature, and water levels.

In standard science experiments, there are controlled variables, independent variables, and dependent variables. We followed this framework as accurately as possible. 

Control (What We Kept the Same)

Controls (controlled variables) are crucial for validating the results. The controls are the things that stay the same. 

Variables like sunshine, temperature, and exact measurements of irrigation are difficult to fully control in an outdoor setting. The soils also come out of the bag with differing textures and moistures, which we cannot control. 

However, we kept the environment as streamlined as possible by growing all the peppers in the same location. The containers were arranged in a close grid to equalize sun exposure as much as possible. We watered them with drip irrigation to equalize moisture delivery.

Independent Variable (What We Changed)

Potting soil was the key difference between every potted pepper plant. Scientifically, the different blends are considered independent variables or experimental treatments. Since we are testing the best soil, each product is its own independent variable. 

To streamline our independent variables, we only selected bagged mixes specifically labeled as “potting mix.” Anything labeled as “garden soil” is designed to be used in-ground only. Potting mix is formulated for containers, grow bags, pots, and raised beds.

We wanted to cover all the most popular brands, so we included products from:

This amounted to 14 different potting mixes to test! These products cover the most widely available brands and products found in the United States. Of course, we couldn’t test every type on the market, but this experiment still offers insights about which blends offer the most “bang for your buck.”

Dependent Variable (What We Tested)

So how do we know which type yielded the best result? The dependent variable is the exact result being tested. We chose pepper plants because they produce fruits (peppers) and we wanted to see which potting mixes actually increase fruit production. Peppers also have less disease or maintenance issues than other garden crops like tomatoes.

As you can imagine, these are a lot of measurements. We didn’t get overly technical like a lab scientist would. Instead, we opted to visually assess the plants just like you would in your garden! Overall, Jacques mostly relied on his expertise to share which plants seem to be performing best.

14 Potting Soil Products Tested + Ranked

Before we left the peppers to grow, we brought in Kevin to make some predictions about which mix he thought would perform best. Right off the bat, he predicted:

• Blends with a lot of woody, sawdust-texture material probably won’t do well
• Lighter colored blends had a lot of peat moss or coco coir
• Darker colors were wetter or had more compost and probably would perform best
• Mixes with extra perlite would probably have mid-grade performance

Check-Ins

We checked in on the plants at three weeks, six weeks, and nine weeks. Major differences were noticeable even at the earliest check-in. Some plants barely grew at all, while others doubled in size. Some plants even looked like they were dying.

The differences in plant growth became more noticeable as time went on, and fertilizers became more “available” for the plants. This timing is different in every potting blend because different types of nutrients are released in different time periods. For example, synthetic fertilizers are often quick-release and become plant-available all at the same time. They could harm the soil, water, or local ecology. In contrast, organic fertilizers are slow-release and provide a gradual, long-lasting nutrient supply.

Clearly, the potting mix makes a major difference in plant growth. You don’t want to choose the wrong blend, or you could waste a lot of money and time.

Without further adieu, here are the overall results of the 14 products tested, ranked from best to worst:

Miracle-Gro Potting Mix (1st Place)

The most shocking result of this experiment was: the most basic, affordable, run-of-the-mill potting mix actually yielded the best results! Miracle-Gro Potting Mix is available at all garden stores and averages $11.88 per cubic foot. 

We were super surprised to find that this plant grew the largest, bushiest, greenest, and healthiest foliage. It also yielded the most peppers in the shortest time. It set 10-12 peppers at different growth stages by week nine. However, this mix has synthetic components. It is not an organic blend. This means it includes quick-release synthetic fertilizers. 

Kevin and Jacques hypothesized that these fast-acting synthetic nutrients contributed to the quicker growth of this plant. A longer-timed experiment may reveal that organic blends produce higher yielding plants because their fertilizer ingredients are longer-lasting. 

Moreover, the fertilizer in this potting mix will taper off with time. Synthetic nutrients work for a quick boost, but they do not provide lasting fertility. Supplemental fertilization would be necessary for future successions or seasons if you wanted to reuse this potting mix.

Vigoro Potting Mix (2nd Place)

At $8.38 per cubic foot, this mix definitely provided the most value overall. The plant almost matched the Miracle-Gro plant’s performance. Although it did not look as healthy from a leafy growth perspective, it had about 8 pepper fruits of various sizes hanging on the plant at the nine-week mark. The plant was also among the tallest and most well-branched. However, like the 1st place plant, Vigoro potting mix also includes synthetic components.

Miracle-Gro Organic Container Mix (3rd Place)

Based on this experiment, the highest quality and most affordable blend for organic growers is Miracle-Gro Organic Container Mix. The 3rd place plant performed excellently. It looked deep green, bushy, branched, and loaded with fruits at various stages of development. Kevin and Jacques predicted that this plant would continue growing and yielding well throughout the season. It had the most flowers and overall healthiest development.

Organic fertilizers like manure, compost, guano, and feather meal take longer to become available to plants. This means they slowly release over time, providing long-lasting nutrients. Note this contrast to the 1st and 2nd place mixes grown with quick-release synthetic nutrients. Our experiment only lasted nine weeks, so we didn’t fully see the results of how each potting mix would perform over an entire season.

Miracle-Gro Moisture Control Potting Mix (4th Place)

The 4th place plant performed similarly to the Organic Container Mix but with slightly fewer fruits. The foliage looked dark green and bushy. It had lots of branching, flowers, and several developing peppers. 

True to its name, this mix stayed consistently moist and drained well. At $16.64 per cubic foot, it is fairly expensive but could still be functional for container gardeners who have less time to devote to irrigation. 

Recipe 420 Potting Mix (5th Place)

For $11.33 per cubic foot, this mix delivered excellent value. This plant was large, green, bushy, and branched. It yielded several pepper fruits by the end of our experiment. The Recipe 420 organic potting blend includes mycorrhizal fungi and slow-release organic fertilizer, which account for the obvious nutrient absorption in the plant. 

Kevin and Jacques predicted that this plant could outpace its competitors if the experiment lasted longer. It showed promise of more flowers and fruits, but it wasn’t as quick to yield as the synthetically-fertilized blends. 

Fox Farms Ocean Forest (6th Place)

Fox Farms is a popular brand on the Epic Homestead because it is middle-of-the-pack in terms of performance and price. At $17.33 per cubic foot, this is on the higher end, but it does deliver a lot of value. The pepper plants were large, branched, and bushy. The leaves were fully green and verdant, indicating that they received plenty of nutrients from the slow-release fertilizer. There were several fruits forming by the end of our experiment and this soil would probably supply enough nutrients for a full season of growth.

Fox Farms is an organic blend with OMRI-approved ingredients for organic farming. It has many trace minerals from ocean sources, such as granulated kelp and fish.

Fox Farms Happy Frog (7th Place)

The second Fox Farms blend we tested was slightly cheaper at $13.50 per cubic foot. This organic blend delivered a similarly sized, healthy looking plant. The leaves were green and abundant. 

There was plenty of branching and foliage, plus several fruits maturing. The blend has enough fertility to get things going, but plants growing in this potting mix may need supplemental fertility in the middle of summer to fuel late-season production. 

ProMix Premium Organic Mix (8th Place)

For $5.24 per cubic foot, this is the cheapest blend for modest quality results. The plant grew taller than the stunted blends below. It had mid-range height, branching, and color. It only produced a few pepper fruits, but it might yield more with supplemental fertility and continued growth.

Nearsource Potting Mix (9th Place)

Only one tiny pepper fruit grew on this plant after nine weeks! This potting mix was fairly disappointing. While Nearsource is pretty affordable ($7.92 per cubic foot), it still didn’t deliver the results we’d expect from a pepper plant at this age. The plant was modestly larger than the lower-ranking mixes below, but it didn’t show any signs of promise for future production. 

We hypothesized that the poor performance might also be linked to the texture. This texture of mix didn’t hold on to very much water. Containers dry out more quickly than raised beds and in-ground beds, so water retention is crucial in this setting.

Sta-Green Potting Mix (10th Place)

The plant grown in Sta-Green was also disappointing. While it had moderate branching and height, the foliage was still pale. There was only one fruit, so overall production was lacking. This blend averaged $8.39 per cubic foot in our experimental area. It may work for budget growers, but still requires supplemental fertility to ensure strong yields.

Malibu Compost Baby Bu’s Biodynamic Blend Potting Soil (11th Place) 

This mix had one of the most surprising results! Kevin initially predicted that this product would yield one of the best plants. Shockingly, it actually grew one of the worst. This expensive blend averages a whopping $21.33 per cubic foot. 

The pepper grown in Malibu Compost’s blend appeared stunted and paled. It had very little branching and foliage compared to the plants above. It grew one small pepper, which would be incredibly disappointing after spending the pretty penny on this bag of potting mix.

These results are proof that expensive does not always mean better! 

Kellogg Raised Bed Mix (12th Place)

One strange thing about this blend was its moisture. It came out of the bag almost soggy. This probably harmed the pepper plant from the start. The seedling remained small, stunted, and pale. It never produced flowers or fruit.

This raised bed mix was one of the cheapest soils we tested, averaging $4.99 per cubic foot. But is it worth the budget-friendly price tag? Based on our pepper results, the answer is no!

Kellogg Patio Plus Mix (13th Place)

The second worst performer was from a cheaper bag of soil, averaging $5.32 per cubic foot. This “patio plus” blend yielded a very wimpy pepper plant with pale yellowy-green foliage that seemed to suffer from a nitrogen deficiency. 

The plant never produced any flowers or fruits. Kevin hypothesized that the texture was so woody, it “locked out” the nutrients. In other words, the fertilizer was never available for the plant to uptake. The seedling never got much bigger than it was when it was transplanted. 

In general, lower-quality mixes have woodier materials like bark and wood shavings. When wood decomposes in the soil, it sucks away a lot of nitrogen to fuel the breakdown process. This can “lock up” nitrogen in the soil, making it unavailable to your crops. High amounts of woody ingredients is a red flag to avoid when shopping for potting soil for vegetables.

EB Stone Potting Mix (Worst)

The worst performer in the experiment didn’t even grow a pepper plant that yielded fruits. The plant barely grew any larger than it was at the time of transplanting. It had small yellow leaves and an overall wilted, “sad” appearance. There were flowers.

This brand costs about $8.66 per cubic foot, making it a mid-level price point potting mix. But based on our experiment, it obviously isn’t worth the money at all!

The Results

Overall, this experiment showed that the best organic potting mix for performance and value is Miracle-Gro Organic Container Mix. This blend was moderately affordable and yielded a tall, verdant, bushy, fruitful pepper plant.

The best-performing synthetic mix was Miracle-Gro Potting Mix, but this blend contains synthetic components and shouldn’t be used in organic gardens. The impressive results were likely due to a huge spike in synthetic quick-release nitrates that might peter off later in the season.

Based on these results, budget growers could get away with something as cheap as the ProMix Premium Organic soil blend (just $5.24 per cubic foot) and add their own supplemental fertilizers.