A few months ago, I had an issue with my robellinis (pygmy date palms) and it was suggested that I add some epson salt to water to give them a magnesium boost. The practice has really helped with those palms as well as my sagos, but I've been wondering... what other plants could really benefit from using the magnesium augmented water on them? What, if any, plants should I avoid watering with this mixture?

By the by, $1.45 for a carton beats $24 for a bag of magnesium fertilizer any day in my book.