There is a big difference between soil amendments - typically organic matter (i.e., compost) added to soils to improve drainage and aeration and to boost soil fertility - and the willy-nilly addition of various elemental or chemical products (supplements) with the hopes that they will do something of benefit to plant growth. The Epsom salts fits into the latter category!! "You must remember that once your garden starts growing, your soil samples go out the window. Nutrients are gobbled up very quickly and the ones found in Epson salts make up a great part of the menu." I have to disagree with this contention.....it is simply not true!! The only nutrient that gets 'gobbled up quickly" is nitrogen and that is because it is 1) the single plant nutrient required in the highest volume and 2) the most mobile of the basic plant nutrients, volatilizing, morphing forms and moving through the soil constantly. With an established landscape and decent soil to start with, it is seldom necessary to ever provide supplemental fertilization if one mulches routinely with a decent organic mulch (acts as N replacement). The exception would be edibles that are harvested, as pulling these plants, which sequester a lot of nutrients themselves, out of the ground removes a portion of the nutrient base. and since a vast majority of edibles are annual plants, their basic nutrient demands are also high to begin with. Epsom salts is magnesium sulfate. Magnesium is seldom lacking in sufficient concentrations in any soil and as a minor plant nutrient, it is needed/utilized in minuscule amounts anyway. Sulfur is also a trace nutrient as well as a soil acidifier and it too is not consumed by plants in any significant quantity and seldom needs replacement. And an excess use of sulfur can alter soil pH more than necessary or desired as well affect how other, more essential nutrients are absorbed. And over application can kill off beneficial soil organisms (sulfur is a fungicide). Rather than buying into the unproven myth (there is NO scientific evidence to support it) that dosing plants routinely with Epsom salts somehow produces some sort of magical, lush growth, it should not be applied unless a professional soil test tells you it is required. And that is the same with applying all manner of other popular (but often unnecessary) garden supplements. Applying these without understanding if a need for them even exists (via a professional soil test) can alter the natural soil balance and create a lot more problems than it solves. The Myth of Epsom Salts. Unfortunately, debunking this and other common gardening myths gets a lot less press than word of mouth or social media promotion of these so-called magic gardening elixirs that really do not do much of anything to benefit plant growth. If you want to be serious about your soils and the health and productivity of your plants, focus on the scientific evidence behind any of these claims. In 99% of them, it simply doesn't exist!!

Just reinforcing wirosarian's point that, if your soil is already high in magnesium, applying substantial amounts of epsom salts is actively harmful. If your soil is low in magnesium, it is helpful. If you have used dolomite lime (the most common kind) to raise the pH of acid soil, that is a long-lasting source of Mg. Epsom salts would be the preferred source of Mg if a soil test shows both low magnesium and a pH above, say, 6.2. Plants use Mg in the chlorophyll molecule. The symptom of Mg deficiency is paleness at the leaf margins with wide bands of normal green along the central vein and several of the large lateral veins. The normal green forms a shape like a stylized drawing of a Christmas tree. The shortage of chlorophyll can reduce overall vigor. I doubt that extra magnesium would cause extra basal breaks. If a soil test or leaf symptoms show Mg deficiency, an appropriate dose would be 2-4 TB of epsom salt every few months.

Exactly....it's only useful if there's an actual deficiency of Magnesium. Folks often recommend Epsom Salts to "green" plants up - what they usually don't understand is that Magnesium acts to make the Calcium in the soil more available. Calcium and Magnesium need to be in the proper ratio for both elements to be absorbed properly. And that's why so many of us prefer to use Dolomitic Garden Lime, which provides Calcium AND Magnesium in the proper ratio at the same time. Otherwise, one would need to supplement the Calcium with something like Gypsum, while also adding Epsom Salts in proper proportion. That's more work than I want, personally, although not especially complicated. Mark is also correct....when leaves yellow, look first to Nitrogen, then to Calcium, then to watering habits....and then finally to the Calcium/Magnesium balance (or imbalance). Josh

In regards to using Epsom Salts, which is magnesium sulfate, I can advise regarding outdoor use in the garden or field but hesitate to do so for greenhouse propigation. My containers of Miracle Grow/Peters are out at the lake but as I recall both contain a quantity of magnesium. So if you are using it to feed seedlings in the greenhouse you likely have enough. Now lets talk about the garden or field crops. Certain areas of the country are rich in mag, others are not. Typically, so called agricultural limestone contains a small percentage of magnesium carbonate along with the calcium carbonate, so if you use this, for example to adjust your soil ph, you are likely to get a good shot of mag as you apply it. I live in far western Pennsylvania, about centered north and south on the state. THERE IS A TERRIBLE SHORTAGE OF MAG IN THE SOIL HERE! So we need to suppliment during fertilization to make up for this. When I was operating my orchard I would add a pound of epsom salts to each 80 gallon spray tank of chemicals. Trees and plants readily absorb nutriants through the foliage--this is referred to as folliar feeding--so by adding it to my insect/anti fungal sprays I got double the bang for my time. (There were some other suppliments added on occasion). It does not take a lot of mag to satisfy a plants needs and once they have enough adding more is just a waste. Fortunately, epsom salts is pretty benign, i.e. does not seem to root or foliage burn, and since it is so readily soluable, rain and or watering pretty well dilutes it and washes it out of the root zone. When I spray my tomato plants to deal with the blight/et al I add Miracle Grow or Peters to the tank mix per direction and also 1 tablespoon of epsom salts, 1 tablespoon of potassium carbonate, and 1/2 teaspoon spreader sticker to each gallon of spray. Once the tomatoes are about an inch in diameter I stop the spreader sticker and just have to spray in the gaps between rains as the sticker is difficult to wash off the fruits. And it works!