Why MiracleGro and Hydroponics Should Never Mix

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February 21, 2014

To the new grower’s mind N-P-K versus N-P-K appears to be the same thing, but it’s not. Nutrients formulated for growing in soil won’t give you good results when you dive into soilless gardening. Fertilizer and nutrients are not the same. A water-soluble garden fertilizer may instantly melt in water, but a hydroponic nute it does not make.

Yes, hydro nutes are way more expensive than MiracleGro, however, even for soil-based growing, MiracleGro is not very good quality fertilizer. It’s just easy and ‘fool-proof’, not to mention you can buy it anywhere – including the dollar store. When was the last time you expected to find top quality stuff at the dollar store? Hopefully you said, ‘Never!’ So why expect cheap stuff to grow you an abundance of great food?

Sure, we’re all looking for the path to feeding ourselves good food at a reasonable cost, and many people’s budget allows no room for error. Before you make the mistake of assuming one is just as good as the other, lets look at the realities here.

Even if you’re using the non-circulating Kratky method instead of a standard hydroponics system, you are about to see exactly why MiracleGro and hydroponics should never mix. You might as well throw away that blue stuff, because what you’re about to see will show you just how well it performs.

Exhibit A

Exhibit B

Here’s a series of videos by MPH Gardener covering the results of his Kratky lettuce bed experiments. He’s always interesting, entertaining, and has something good to share. The first trial he ran using Masterblend compared to MiracleGro (or Miracle Grow as some folks type it). The next grow he ran water-soluble Masterblend against Fox Farm Grow Big, and Chem-Gro Hobby Formula. The winner for best performance is?


If you’re wondering about the pH level differences he had on that last grow between the different nutes he used, you’ll find them listed in the bottom of the info section HERE.

Amber

Amber

Contributing Writer at Garden Culture Magazine
The garden played a starring role from spring through fall in the house Amber was raised in. She has decades of experience growing plants from seeds and cuttings in the plot and pots.
Amber

20 Comments

  • Fish water and a hydroponic-specific nutrient are going to have the full range of nutrients necessary for a plant to grow. Miraclegro contains only 3. Plants need 16 or 17 nutrients (depending who you ask), and get only 3 from the air. This means means you are missing 10 or 11 with miraclegro. Of course you can’t substitute an incomplete nutrient mix for a complete one, but if you add the missing nutrients it will work great. You are spreading half the story and trying to pass it off as science. How about tell the whole story instead of just confusing people even more?

    • Hi Anthony,

      It certainly wasn’t our intention to confuse people, or to tell half the story, but thanks for adding your thoughts to this page. People have to start somewhere at discovering that what works for soil-grown plants is not going to work in soilless growing. At the same time, there are a lot more things in the soil that plants need besides nutrients, like their working relationship with the microorganisms that exist in healthy soil, which make far more than a only 16-17 nutrients available to them. That number is only what has been definitively identified by science and will do a decent job of growing plants in hydroponic situations, though it is coming to light that plants really need more to be at their most efficient productiveness.

      This post was written to help beginners understand that you can’t just toss in a basic garden fertilizer and expect awesome results from your hydroponic garden. No mention of science was made, however, if you’re interested in the more technical nature of nutrients, you might want to start reading our print publication where a lot of intense knowledge from seasoned industry veterans is published in every issue. You’ll find it at discerning progressive gardening shops all over North America, the UK, and Australia/New Zealand. If you can’t locate a hard copy, we have digital versions available online, and soon with the launch of our newly designed website, every issue in print will be accessible here on GardenCulture.net.

  • MiracleGro (and other related fertilizers) actually do contain several other nutrients beyond the “big 3”: nitrogen, phosphorous, and potassium (N-P-K). Briefly, they also have (in varying proportions) sodium, borate, molybdnium, iron, manganese, zinc, copper, sulfur, and chlorine. Notably absent, and what I would surmise is the MAJOR issue, are calcium and magnesium. The other problem may be that it has minimal buffering capability, so the pH could go all over the place.

    So yes, MiracleGro all by it’s lonesome is terrible for hydroponics. That’s not because MiracleGro is bad bad bad, it’s simply designed (quite well, actually) for use on plants in soil, and there it does a great job. There, it can use the other minerals to get some Mg and Ca, as well as buffer pH.

    I would be very curious to see what happens if you were to use MiracleGro and 1) supplement it with some Mg (maybe from epsom salt) and Ca (lime, gypsum, or calcium nitrate), and 2) watch the pH.

    All told I’m not sure if it’d be any cheaper. An 8 oz bottle vs. 32 vs kilogram of powder are sometimes within a few bucks of each other–it’s all probably dependent on who’s selling it–but it would tear down the notion that hydroponic nutrients are magic and only some companies can make ’em.

    • Hi Nick,

      Yes, in a lot of people’s minds when they are hampered by limited knowledge about what plants need, hydro nutes can seem like magic. It all comes from our thousands of year of growing in soil, and so many not being connected with it as a means for producing food anymore.

      Miracle-Gro does work great… on soil-grown crops, though it is not the best quality of fertilizer, and does nothing to promote or support the life on the soil. It is more of a replacement for microorganisms, and this makes the gardener a slave to feeding plants when a healthy soil does this on it’s own. But as you have said, it is lacking some important things for hydroponics that traditionally grown plants would normally get from the soil.

      Since hydro crops are totally dependent on nutes, it would be interesting to conduct a study on balancing the nutrients that Miracle Gro has versus what is needed to add. If you decide to tackle that – please contact us. I’d love to publish your discoveries here on the website. And I suspect as you do that once the formula is right it would be no ‘cheap’ solution to saving money on hydroponic nutrients. Still it would be interesting to see what happens.

      Thanks for adding to the conversation!

  • I read the article and the comments. None of you guys got to the point. It’s not hard, just chemistry. If you compare Miracle grow with Maxi Gro, you’ll get the answer. The pH, trace elements are not really the big issue here. My biggest concern is that the major form of nitrogen in miracle grow is urea, which is organic form of N, and they cannot be uptaken by plant directly. Nitrate and ammonia will work fine, that’s what most hydroponic mix use. Miracle Gro is great, it not only fertilize the soil, also adding amendment to soil and other trace elements.

    • Hi Kun,

      Having used both forms of Miracle Gro for many years, I agree, it’s great for growing in soil… at least until you start learning about how much healthier other forms of soil nutrients are.

      Yes, it’s just chemistry, Miracle Gro was formulated for plants growing in the ground – not water. But a lot of newcomers to growing their own food with hydroponics don’t understand that chemistry stuff. They won’t realize why their grow wasn’t so hot, and many will just up and decide hydroponics is too hard to do. They have no idea that there are extremely different forms of nitrogen, and many people want to accomplish much using the cheapest trick possible, instead of investing in the right stuff. That was the point behind this article.

  • i’ve used miricale grow on outside plants and have had great results. looks like hydroponic not so much.

    • Hi Sheldon,

      Yes, the stuff works great on flower and veggie garden plants, but it does not do the soil food web any favors. Only organic inputs promote beneficial microorganisms, while synthetic fertilizers, which Miracle Gro is, kill off the soil food web and make your plants totally dependent on your fertilizer as well as lowering their immunity to pests and disease.

      And as the discussion so far in comments has revealed, you could only use MiracleGro in hydroponics if you know what additives you need and at what ratio to make up the elements it is missing that your hydro crops need to live and perform.

  • could you please help me decide which fertilizer is best for my flood and drain system and tomatoes? Love your post. Mike. God Bless

    • Hi Mike,

      First, you want a good mineral-based brand. No organics. If you’ve got a tight budget, NutriPlus is a good but inexpensive choice. Need any other help with your tomato crop, Eric would be happy to give you some pointers. He grows a mean hydroponic tomato. You can contact him at: eric@gardenculturemagazine.com.

    • Detroit jackson April 22, 2016

      Maxigrow and maxibloom. Hands down. Peters is great too. Hell yes Im bRinging back a dead post!

      • Hey Detroit,

        Thanks for your input. It’s not really dead, just snoozin’ 😉

  • Im using miracle gro + sea salt + hydrogen peroxide and a pinch of cinnamon. the roots are big and off white! very healthy!

  • Can anyone tell me if the calcium in hard water is a benefit to hydroponics

    • Hi Wayne,

      It’s not beneficial. Too much calcium can cause nutrient imbalance because it ties up other elements. Either use a reverse osmosis filter on your tap water, or use distilled water.

      The amount of calcium in water drawn out of your faucet will vary. On a tankless well where the water is running straight from the source, the longer the water runs, the more spread out the mineral content will be. If the well has rested for any length of time, the concentration of minerals will increase. With a holding tank, your calcium content will be higher, because of settlement that collects in the tank. Most people have a tank on their wells.

  • I use Miracle-Gro in my hydroponics solution and it works fine. But I don’t use it by itself and I only use it half strength. I also mix in some extra liquid cheleted iron with micronutrients, potash, phosphate, magnesium, sulfur, calcium, and chloride, along with a little aged urine for some extra nitrogen. My plants are growing great – they love the stuff! I have them in a “soil” mix of 2/3 coarse perlite and 1/3 vermiculate, in 20 gallon plastic boxes I bought from Wal-Mart and I just water and feed as needed – just like in soil. No pumps, storage tanks, feed lines, or other bulky equipment beyond a solar powered hydrometer telling me when to water. The stems are strong, roots healthy, leaves a nice dark green – no problemo! I also use unfiltered (city) tap water and stopped worrying about ph a long time ago – it’s always 8 right out of the tap and around 6.5 – 7 after mixing in the nutrients. Once a year I flush the substrate with distilled water to remove any build up of mineral salts, and then go right back at it for another year. The vermiculite is great for holding moisture and the perlite provides plenty of air space for the roots. In fact I can put 10 gallons of water in a 20 gal box with no water settling to the bottom – the vermiculite absorbs and holds it all. I can grow plants like tomatoes and chili peppers much closer together than I could in the ground with great results because there’s no competition for nutrients or moisture so I get maximum return for the volume of substrate used.

  • JACK BRONDWIN June 6, 2018

    Hey Terry,
    I’m fascinated by your comment. Can you share with us what do you add and how much so we can duplicate your recipe. I love that you are adding urine as a nitrogen booster. Please do not not any details.
    Thanks
    jack

  • Although I would agree that MiracleGro is, by itself, less effective than Masterblend or fish water, I find your study to be unscientific. The MPH gardener used a commonly edible food plant, leaf lettuce. Who knows much about mint except that it can be a soil grown nusience? Ever eat a mint and tomato salad? I’m keeping an open mind.

    From the top, I was skeptical when water it was said that water soluble MG “melts” in water. It does not melt. It dissolves. Melting of any solid occurs when it goes from a solid to liquid state. Melting usually involves higher temperatures.

    Even after all these years, knowledge about hydroponics is evolving. So, all experiments which contribute to the knowledge base are beneficial.

    I’m not without my sense of humor tonight. Any advice on what to do with that bald spot on the crown of my skull? That might require a “miracle growth.”

  • Hello, Well I started my hydro plants in a 55 gallon tote and didn’t have time to wait for the proper minerals needed. So I did use miracle grow as a quick and easy. Lol. I won’t lie? Idk what is missing in the difference between the two ? But my miracle grow plants are actually growing amazing. They are prob a foot and a half taller then the plants I have in the ground and the stems are much thicker. I often pull the plants out of the water to prune them, and the roots are beautiful and clean. It’s still early in the season …. but I have a ton of tomatoes growing right now compared to the ones in the ground. I will be changing to the proper nutrients on my next water change. But….. I don’t think it makes a difference personally.

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