A  The key words here are trace elements. Too much can be as bad or worse than too little; a trace is fine, but a tad may be toxic. For this reason, you would not need to add a formulation like STEM to your current fertilizing program. The only proviso I might add is that an occasional application of magnesium sulphate (epsom salts) on its own is probably beneficial. Many European growers consider magnesium a macroelement rather than a trace element and apply it at correspondingly higher levels. For intermittent fertilizing, 20 ounces of magnesium sulphate dissolved in 50 gallons of water would never cause problems. — Carol Holdren, AOS Volunteer, International Orchid Center, Deiray Beach, Florida (e mail choldren@concentric.net).