Garden & Greenhouse May 2018 Issue | Page 44

FEATURESTORY by Ray Barkalow Magnesium Supplementation for Orchids M agnesium is a major building-block in the formation of chlorophyll, and its role in the functioning of plant enzymes to produce carbohydrates, sugars and fats. Knowing this it is easy to understand the importance of regularly providing magnesium as part of an or- chid feeding regime. Unfortunately, not all fertilizers provide magnesium, so we may find a need to add it via some sort of supplementation. Fortunately, that is easy to do using inexpensive Epsom Salt purchased from your local pharmacy. 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 • www.physan.com 44 But of course, we need to consider just how much to use, and how often to do so. First let’s look at the chemistry. Epsom Salt is a magnesium sulfate mineral – giving a double benefit, as sulfur is a plant nutrient as well. (Its name incidentally, comes from a bitter, saline 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 sept hydrate, MgSO4•7H2O. By mass, that means that Epsom Salt is approximately 10% magnesium and 13% sulfur, with the balance being hydrogen and oxygen. Many will acknowledge that 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 fer- tilizer solution concentration of 125 ppm N, the label tells us to use 3.55g of fertilizer to make up a gallon of solution. That means, therefore, that the gallon contains 3.55g x 2% = 0.071g Mg. If the fertilizer you are using contains no magne- sium, 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. www.GardenandGreenhouse.net May 2018