Note : Since these recipes are from American sources, one gallon is probably
128 oz. (3.5 L) vs. 160 oz. (4.55L) for an Imperial gallon.
Can I mix Epsom salts with my regular fertilizer?
Concerns were raised at our recent MOS meeting whether there would be a solubility interaction between MgSO4 and the fertilizer, resulting in the formation of a precipitate. The information in the section above suggests that you can mix these chemicals without a problem. However, I will offer (a) a practical way to determine if an interaction occurs between your brand of fertilizer and MgSO4; (b) if a precipitate does occur, what it is likely to be; (c) what solubility theory says about precipitation reactions and the effects on the Mg2+ ion's delivery

to the orchid roots.
(a) Make up your fertilizer solution and add the desired amount of MgSO4. Stir well. Then fill a tall, clear glass tumbler (jar) with the mixed solution. Next, go into a darkened room and shine a flashlight beam through the glass tumbler, as shown in the diagram. If there is a precipitate in the liquid, you will see the light beam in the liquid. (The fine solid particles will scatter the light beam and make themselves known.) This test is very sensitive-even a small amount of suspended matter will reveal itself.
(b) In the
Handbook of Chemistry and Physics I checked for possible interactions of magnesium with other components of the fertilizer. The only significant interaction would be between the magnesium ion, Mg2+, and the phosphate ion, PO43-, of the fertilizer. Magnesium

do your own experimentation with the amount and frequency of Epsom salts application. The information below can be a good starting point for your own experimentation. I have selected recipes based on whether you like to fertilize at every watering, once a week, or seasonally.
1. One-half teaspoon of Epsom salts to one gallon of fertilizer solution every time you water, (3).
2. If you fertilize your plants once a week, then use one tablespoon of Epsom salts per gallon of fertilizer solution, (1).
3. Bob Gordon recommends five teaspoonfuls of Epsom salts per gallon applied twice in a row in October for Phalaenopsis orchids.

VOLUME 1, ISSUE 2

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