That little packet of dark powder you are coerced into purchasing along with your clover seed can be mystifying. It only weighs a few ounces, and it has to be kept cool and dry and managed like a living pet (it is, after all, alive). Plus it invariably gets all over your hands and clothes. What is it, anyway, and is it really necessary? The short answer is yes, it is necessary in the vast majority of cases, if you want to do everything possible to stack the deck in your favor. – See more here.