Ask a Question forum: How to use epsom salts for plants?

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Name: Alda yarbrough
Tx. (Zone 8a)
Through God, all things are possib
Apr 25, 2015 7:55 AM CST
For what do you use Epsom salt on plants ? Can it hurt plants and how to apply. cillay
Name: Anna Z.
Monroe, WI
Charter ATP Member Greenhouse Cat Lover Raises cows Region: Wisconsin
Apr 25, 2015 7:57 AM CST
I just throw some on the top of the soil and water it in. I use it on my huge brugs...........24 inch pots. I put about 3 or 4 handfuls on top and water.
Name: Elaine
South Sarasota, Florida (Zone 9b)
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Apr 25, 2015 8:16 AM CST
It does depend upon the plant, of course. Epsom salts is magnesium sulphate and is very soluble. Magnesium is a component of fertilizer as a trace element, so it's a supplement, not a substitute for fertilizer. But some plants (like brugs) use a lot more of it than the 'trace' they get in fertilizer. Big, fast growing plants that really like it want a continuous supply, so you can sprinkle it on the soil (but a heavy rain will dissolve it fast) or dissolve it in a watering can every week or two.

I dissolve it in water and water it in, for my big plants in pots and for shrubs in the spring when they are really growing fast. About 3 tablespoons to a gallon. For my orchids, I add it every time I spray them with orchid fertilizer. They love it, especially in cold weather. But I only use a couple of teaspoons per gallon on them as they are foliar feeders, and soluble salts left sitting on the leaves can be a problem in hot weather here.

Palms really like it as well. You can sprinkle it around the palm on the ground, but I buy a specially formulated palm fertilizer that has extra magnesium in it, encapsulated to release slowly so I don't have to remember to water the palms with the watering can.

I'm not absolutely sure, but I think it would be pretty hard to harm a plant with too much Epsom salts, since it is so very soluble. But in high doses it could alter the pH of the soil temporarily, so I still wouldn't put a whole bunch of straight crystals on a small plant. For small potted plants, dissolve it and water it in.

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Name: Ken Ramsey
Starkville, MS (Zone 8a)

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Apr 25, 2015 8:45 AM CST
I use it as a solution, 1 tbl. per gallon, and use it on my orchids every 2-3 months.
drdawg (Ken Ramsey) - Tropical Plants & More
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Name: Sue
Ontario, Canada (Zone 4a)
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Apr 25, 2015 9:08 AM CST
Plants need a number of essential nutrients. The major nutrients (macronutrients) are nitrogen, phosphorous and potassium. There are other macronutrients, often called secondary macronutrients, which are calcium, magnesium and sulfur. In addition to these, plants also require some nutrients in very small amounts, and these are called micronutrients or trace elements. These include zinc, manganese, boron, copper, iron and molybdenum.

Epsom salts cover two of the secondary macronutrients, magnesium and sulfur, as Elaine mentioned. Magnesium is often not included in general fertilizers. If magnesium is deficient in your soil you will likely see what is called interveinal chlorosis on the plants' leaves. This is where the leaf gets pale but the leaf veins stay darker green. This can be confused with a micronutrient deficiency (iron and/or manganese) but magnesium deficiency is more likely to start on the older leaves. If your soil has a high pH then these symptoms would more likely indicate iron or manganese deficiency than magnesium, magnesium deficiency being more likely on an acidic soil.

If you have an acidic soil (and I believe that at least parts of Texas are the opposite and tend towards higher pH) there are better ways of providing magnesium than Epsom salts.

If you're adding Epsom salts for a reason other than because there is a magnesium deficiency, say because it may enhance flower colour, I agree with Elaine it probably won't do any harm even if it is unnecessary based on the amount of magnesium naturally present in the soil. It is supposed to have little or no effect on soil pH. If you have an acidic soil and aren't growing plants that like a low pH, you might want to look at dolomitic limestone instead if you need to supply magnesium.

[Last edited by sooby - Apr 25, 2015 12:28 PM (+)]
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Wichita, Ks. (Zone 6a)
Garden Ideas: Level 1
Apr 25, 2015 12:33 PM CST
The conclusion from Dr. Chalker-Scott's review of literature (as she says, "scientific and gray") on Epsom salts. The embedded link will take you to her WSU page with connections to her other papers on gardening myths.

"The Bottom Line
The urge to use common household products as garden fertilizers and pesticides is compelling
for many consumers who want simple, cheap approaches to landscape management.
However, the use of any chemical in a landscape should be thoughtfully considered:
o Is it necessary?
o Can it cause damage?
The science behind the use of Epsom salts is only applicable to intensive crop production in
situations where magnesium is known to be deficient in the soil or in the plants. It is
irresponsible to advise gardeners and other plant enthusiasts to apply Epsom salts, or any
chemical, without regard to soil conditions, plant needs, and environmental health."
(A complete bibliography of the scientific and gray literature on Epsom salts is available by
email from the author.)
Dr. Linda Chalker-Scott, PhD
Associate Professor and Extension Urban Horticulturist
WSU Puyallup Research and Extension Center
7612 Pioneer Way E
Puyallup, WA 98371
Phone: (253) 445-4542

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