He Does Not Know How
"He also said, “This is what the kingdom of God is like. A man scatters seed on the ground. Night and day, whether he sleeps or gets up, the seed sprouts and grows, though he does not know how. All by itself the soil produces grain, first the stalk, then the head, then the full kernel in the head. As soon as the grain is ripe, he puts the sickle to it, because the harvest has come.”"
— Mark 4:26-29
This is the only parable that appears in Mark and nowhere else. The farmer does two things in it: he scatters, and much later he reaps. Everything in between happens without him and against his understanding. Mark says plainly that he does not know how. The growth is real and it is not his doing.