To add to what Reaper said, I personally NEVER add it to liquid ferts, but instead apply it as a foliar feed when and if I see the tell-tale stripes of Mg def cropping up.

The only plant I use it on is roses- for some reason, it causes grafted roses to grow more vigorous shoots from low on the plant.
stinkyattic Reviewed by stinkyattic on . Epson salt well i read the back of an epson salt bag(the shit you put in bath water to make your muscles not hurt) and it said you can use it as a plant nutrient or enhancer or something. it didnt say weed of course but it did say it was great for tomatoes and shit... anyone ever tried it? Rating: 5