Really necessary, because our water comes from a reverse osmose device. Unfortunately I bought it a little bit too late. For my next plants I will give it at water from beginning
@JamesBarre, yes, thats true. But I cut really carefully and so the final weight is however a little bit less than I hoped for. Otherwise they hadnt a tent from beginning, the first 4 weeks they get only sunlight in spring, so I think I cant complain;))