If you use peat directly out of the bag without first soaking and rinsing it to remove minerals, then you may be introducing an undesirable concentration of minerals via the peat. Some brands (and even some batches) vary in the amount of mineral content, and you can be playing roulette with your plants if you don't wash the peat before using it. I strongly recommend purchasing an inexpensive ($20 or less on Amazon) TDS meter and soak the peat you use (new stuff, from the bag/bale) and then squeeze out the water after a day of soaking, and measure the TDS of that water. That should be a clear indicator whether or not the peat has significant mineral content, and determine whether or not it needs "washing" before use. I have seen some significant mineral content in certain bales I have bought, and so now I wash all peat before using it.
Originally Posted by IceDragon