First and foremost, Epsom salt is not your everyday seasoning like rock salt, sea salt, table salt, which are all variants of the same thing sodium chloride NaCl. It is the common name of magnesium sulfate. And you won't want to add it to your food like any seasoning, because as the Chinese name suggests, it's a laxative and often use in conjunction with lemon juice as a folk remedy for colonic cleansing. It's also a component of bath salt among some of its other uses.
Magnesium is essential to the formation of the green stuff, chlorophyll, in plants. The photo shows the difference Epsom salt made to our chilli pepper. We use 1tsp of Epsom Salt for 1 to 2 litres of water.
You probably won't find Epsom salt in your average garden centre. Go to your local pharmacy for these. Of course you need the Chinese name, otherwise most local wouldn't have a clue.