Is Epsom salt good for orchids?

[Ross]

Originally Posted by Ray

Epsom Salts is magnesium sulfate septahydrate (MgSO4.7H2O).

Magnesium (Mg) is a critical structural component of the chlorophyll molecule and is necessary for functioning of plant enzymes to produce carbohydrates, sugars and fats. Magnesium-deficient plants show yellowing between veins of older leaves, and they may appear limp.

Sulfur (S) is a structural component of amino acids, proteins, vitamins and enzymes and is essential to produce chlorophyll, so a deficiency usually shows up as light green leaves.

As was stated, magnesium is in most municipal and private well water supplies, and most fertilizers contain sufficient sulfur. If you have a complete fertilizer, it is unlikely that you'll ever see deficiencies in either, and if you want to add it, do so in small quantities as a supplement to your fertilizer, not as a replacement.

The GreenCare MSU RO formula - probably the most complete fertilizer on the market - contains 2% Mg and about 0.1% S by weight, while Epsom Salts is 10% Mg and 13% S. That would suggest to me that if I wanted to add it, I should probably not bother using more than about 1/5 of the amount of fertilizer I use.

I have added more as experiments - one time I went as high as two tablespoons per gallon - and I ended up with the strangest "zebra-striped" plants.

One thing that is nice about Epsom Salts is that adding it does not affect the pH of your nutrient solution.

Thanks, Ray. Right on the target as usual