Epsom salts add magnesium to the soil in a form that is available to the plants in alkaline soil. It will also lower the pH a small amount. It may not be a good idea to add to a vegetable garden since too much magnesium can be a problem in vegetables (if the plants need it, you can add a little, but be more careful around vegetables). If your plants have magnesium deficiencies, Epsom salt can help provide the magnesium they need. If you search chlorosis and magnesium, you should be able to find pictures of plants that are suffering magnesium deficiencies. It may be difficult to tell the difference between magnesium deficiencies and iron deficiencies, so try to find information on both.

Magnesium issues can be a problem on some plants and a cause of chlorosis on unfertilized or underfertilized ones occasionally and hardly a myth, but certainly quite uncommon. You can look up the symptoms online, but as a general rule, any time plant leaves start to yellow, it's time to do some digging (so to speak!) So I keep a small bag around and have for the last decade, but I can absolutely state I've used about five ounces out of it in that decade, including the entire property of 12,000 square feet total. If you're using most versions of Miracle-Gro to fertilize, Mg shortages shouldn't be much of an issue, nor should any lack of green leaves. But still, underfertilization may occasionally rear its ugly head. As a general rule, low nitrogen, iron, or magnesium problems can all be a cause of yellowing leaves (among many others, but those tend to be the primary resource-related ones, in that order), so definitely go investigate if these are showing up on your plants. But never, never blindly toss Epsom salts or any other resource on plants just to cure a problem that isn't there. Magnesium can cause tightening of soils, even very loose and sandy ones, and that's the last thing you want in a succulent pot or any other soil. Too much magnesium also make it harder for the plant to absorb some other resources if amounts rise too high due to simple resource antagonism. I tend to follow the "feed weakly, weekly" method on most plants during their growing seasons because simply put, it works and maintains a constant regular flow of nutrients. If the plant doesn't want it, it has ways of letting you know. If it does want it, it also has ways of letting you know--usually by not growing and turning funny colors. I'd rather avoid that, thanks. But I also tend to avoid that on anything but N, P, and K and only allow maintenance levels of anything else to avoid some of the discussed problems above. So you can walk a fine line over the years even feeding regularly. That's why regular repotting is recommended--and why some of us do some organic feeding even in our pots.

Thanks Matt ... I'm going to think this over for a while ... its just not that big of a deal to spray twice. My fear is not necessarily causing damage ... but reducing efficacy, which may be hard to measure when just doing a branch.

" How would I know if there is a magnesium deficiency in the soil? " Unless you are skilled at evaluating nutrient deficiencies just by sight - and few home gardeners are - you would need to have a soil test done. Yes, it's a myth :-) Various online sites tout all manner of 'magic elixirs' for the garden that promise your plants will grow bigger, healthier and with better flowering. Most of them are just crap. Magnesium sulfate - Epsom salts - does have value but only for very limited circumstances. There is probably more junk gardening information available online than there is accurate information of value. You need to learn how to discern the difference. Or better yet, educate yourself.....learn about your soil, learn about fertilizers and when they are needed and learn about what the plants you are growing need to be healthy and productive.