Kids say the Darndest Things

"Girls make milk and boys make fertilizer." EJ's matter-of-fact demeanor belied my confused stare at him as I tried to understand what I thought he had just said. He was sitting between his brother and sister at the counter munching on his lunch and talking to me through the cacophony of short-order request on all sides, so I wasn't sure I heard him correctly. I understood the "girls make..." part, but was unsure of what it was "boys" make. He calmly repeated his observation over again until both his mother and I understood what he had said. Now the only thing left to understand was what he had meant.
I decided that he was making a joke of some smelly little boy variety and asked whether he had been camping lately thinking exposure to Boy Scout-type jokes was the origin of the observation. Hal piped up and said he had been camping. EJ just looked confused. Now it was his turn to wonder what I meant by my camping comment.
Meantime "Girls make milk and boys make fertilizer" was still an amusing comment which I repeated to Grandpa when he came home. We both made the colon connection and shook our heads in the "Kids say the darndest things" way.
Later his mother told me she had figured out what he was trying to say. She had been teaching him "Birds and Bees" for the six year old, telling him that males fertilize the eggs. His mind reduced the info into milk/fertilizer comment.
I do now understand why he said what he said and still consider it amusing But I am worried that when his reading skills improve he will recognize the writing on the green Ortho box on the shelf in the garage and conclude that Grandma has "fertilizer" envy.