Epsom salt is a type of water soluble fertilizer in the form of crystal powder that is easily dissolves in water.
It is able to increase the nutrients absortion rate of the plants making the leaves look greener and increase the efficiency of photosynthesis.
For watering usage, dilute 2 tablespoon of Epsom Salt in about 4litre water, and water your plants as usual.
For direct usage, add half tablespoon of Epsom Salt onto your plant media and water it accordingly.
Use it once a month.