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I am a little torn over Miracle grows fertilizer that they sell. Example of what I am talking about here. I have known this stuff to be good because it can supply 24-8-16 (NPK) to plants, so it takes little to help the plant.

But now I am hearing that it leaves behind salt, which will, of course, build over time. I got this from my Master gardener meeting last night.

With the little am I now aware of with Miracle grow, I am not sure if this is more harmful than it is good over-time. I would love to know of any and all cons of this product.

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  • That N seems a little high to me, compared to K. Your plants will want to grow lots of foliage, but less in the way of roots. Schulz African Violet food 8-14-9 at 7 drop per quart distilled water reads 110ppm (directions->use every time you water) I'd look for a Miracle Grow with a more balanced NPK. They do make several formulations. 100 to 150ppm can be used every time. Heck, my tap water is 280 in Calcium salts, and that's not causing visible salt buildup.
    – Wayfaring Stranger
    Mar 3, 2019 at 17:43

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There is a lot of confusion on the subject of salt and fertilisers - when we hear 'salt' we think of the sort of salt that's used in food and which we wouldn't want on our plants, in the main. However, the term 'salts' (as opposed to salt) is a chemist's terminology for various elements in a particular form which are in fertilisers, particularly soluble ones, and it has nothing to do with table salt. This https://www.gardenmyths.com/salts-dont-kill-plants-or-microbes/ explains it really well and is definitely worth reading.

White crusty deposits on soil or round the top of pots can be due to 'hard' water, which contains lime; when it dries out, and over time, it becomes very obvious in the form of limescale.

I do agree, though, that Miracle Gro is wasted on plants in the ground - it is most useful for contained plants.

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  • thank you for that website, it was SUPER helpful! It answered all my questions!
    – Ljk2000
    Mar 22, 2018 at 19:53
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Unless you are watering your plants with distilled water it is likely you will get far more salt from your water and/or potting soil than from the fertilizer. You can also get white "crust" from calcium, etc. I did a quick search and found a lot of anecdotal information that MiracleGro makes your plants salty. None of them supplying any scientific or even pseudo-scientific explanations of what makes MicracleGro, a) cause salt to accumulate, b) able to remain in business selling what some are saying is plant poison.

I can't say yes or no with any certainty, but I'm skeptical.

I make my own fertilizer. I grow cactus and urea nitrogen is useless to me. I get ammonium sulfate, potash and some high-potassium blooming fertilizer (usually 0-50-0). Grind it up and mix it with my water.

FYI: I haven't used MiracleGro for many years, since I started making my own fertilizer more suited to the dry media plants I grow.

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The only point in using this product is when you're growing containerised plants. There you are completely responsible for their nutrients, and you can't be sure you are otherwise supplying all the plant's needs.

Whereas in the ground you can just provide compost and the soil microbial life takes care of the rest for you unless there's some serious imbalance which should be detected by a soil analysis.

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It is very expensive compared to getting about the same composition in a 40 # bag. But it has higher water solubility; This is an advantage if you are in a hurry or using hydroponics. I use "starter" for everything ; water soluble, 9 -45 -15 , aka Peters. I use a solution for pots and sprinkle dry on the ground at certain plants , occasionally supplement it with a high N lawn fertilizer. ( 25 # bag on the internet). A wide variety of plants do well .

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My Anthurium was diagnosed recently with salty soil: all I have ever used is miracle grow in a good potting soil. I have now leached it repeatedly with distilled water and rainfall, and do not plan to use miracle grow in the future, especially not on container plants. The brown spots on the leaves are gone--they were appearing on both new and old leaves before. I have a nice crop of brilliant green leaves now.

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