Hi, I've been reading some info on using epsom salts in your grow. Is it something to use on a regular basis or just when you see problems occur? Does anyone here use it regularly or sporadically? Is there a tell from your plants to when its needed? In flower or in Veg? so many questions any information would be great, thanks.
I would only use it in a soil grow if there were signs of magnesium deficiency. 1/4 tsp/gal for minor deficiency, 1/2 tsp/gal or significant def.
If your tap water had an imbalance of Ca & mg (which should be 2:1 to 4:1 ration, epsom salt could be used to balance that. If you used reverse-osmosis water which has almost no minerals in it, epsom salt and gypsum could be added to it to get a good ratio and about 150ppm before adding nutrients. But, it's more common to mix tap water into the RO water to get that (when people have very high ppm tap water).
People who grow using LED grow lights sometimes add mg to every feeding because they feel the light causes the plant to use more mg. I grew with such lights an never did that. It may depend on the light.
I made the attached PDF for myself (to reference when I need to use epsom salt or gypsum).
Hyroponics growers use epsom salt a lot. They calculate their nutrients using a free program called Hydro Buddy. They'll use raw products to get the percentages they need. Epsom salt is something they'll use to get where they want to be. In soil, it's expected Ca and Mg will exist in the soil (dolomite lime.).