I recently added gypsum to my soil to combat heavy clay soil then planted a snowfake hibiscus and a syzygium, the hibiscus died and the syzygium struggle but is ok now. Does gypsum effect plants?
Mostly no, but if large amounts are added to the soil, it can create a few nutrient deficiencies. Gypsum can reduce the amount of iron, manganese, magnesium, phosphorus, copper and zinc a plant can take up, but it would have to be a pretty large amount of gypsum to do this.
Gypsum is much like any other soil additive. The right amount is good, but too much can cause problems.