Garden & Greenhouse July 2017 Issue - Page 48

FEATURESTORY by Ray Barkalow Magnesium Supplementation for Orchids M agnesium is a major building-block in the formation of chlorophyll. Its role in the functioning of plant enzymes to produce carbohydrates, sugars and fats leads to the importance of regularly providing magnesium as part of an orchid feeding regime. Unfortunately, not all fertilizers provide magnesium, so it is sometimes nec- essary to add it via some sort of supplementation. For- tunately, that is easy to do using inexpensive Epsom Salt purchased from your neighborhood druggist. But of course, we need to consider just how much to use, and how often to do so. Epsom Salt is a magnesium sulfate mineral – giv- ing a double benefit, as sulfur is a plant nutrient as well. (Its name incidentally, comes from a bitter, saline MULTIPURPOSE GREENHOUSE DISINFECTANT & DISEASE CONTROL • Disinfect pots, trays, benches, tools, etc. • Algae control on walkways, pots, evaporative coolers, soil • Spray on plants to control bacterial, viral and fungal disease • Excellent wetting agent • Cost effective, pleasant odor and environmentally friendly MARIL PRODUCTS, INC. 15421 Red Hill Ave. • Suite D • Tustin, CA 92780 USA 714-544-7711 • 800-546-7711 • 48 spring at Epsom, Surrey, England, where it was found to be useful as a bath salt and laxative back in Shakespearean times.) The form that can be purchased at the drug store is the septahydrate, MgSO4•7H2O. By mass, that means that Epsom Salt is approximately 10% magnesium and 13% sulfur, with the balance being hydrogen and oxy- gen. Many will acknowledge that the Greencare Orchid Special formula for RO water – the original, so-called “MSU” fertilizer – is a very good, complete fertilizer formula. It contains 2% Mg in its dry form. In order to achieve the commonly-recommended fertilizer solution concentration of 125 ppm Nitrogen, the label tells us to use 3.55g of fertilizer to create a gallon of solution. That means, therefore, that the gallon contains 3.55g x 2% = 0.071g Magnesium. If our fertilizer contains no magnesium, and we want to add that same 0.071gram per gallon using Epsom Salt, we would need 0.071g ÷ 0.10 = 0.71g of Epsom Salt per gallon of solution. Since most growers don’t have a lab scale handy to measure that, let’s convert it to a practical volume measurement. The bulk density of granular drug store Epsom Salt is about 1.05g/cc. That means that we would need 0.71g ÷ 1.05g/cc = 0.68cc per gallon. As there are approximately 5 cc (or ml) in a teaspoon, that’s just a bit more than 1/8 teaspoon (0.136 versus 0.125 – 9% more). July 2017