“For the earth bringeth forth fruit of herself; first the blade, then the ear, after that the full corn in the ear.”
All by itself the soil produces grain — first the stalk, then the head, then the full kernel in the head — the self-generating growth follows an inherent order: stalk, head, full kernel. The stages are not random but sequential, each one building on the previous, each one necessary for the final result. The farmer does not need to know the biological mechanism to trust the sequence. The kingdom's growth follows its own divinely ordered stages, and the disciples can trust the sequence even when they do not understand the mechanism. The patience required of disciples is not passive waiting but trust in the seed's inherent, divinely-given growth power.
Church Fathers on Mark 4:28
The kingdom of God is the Church, which is ruled by God, and herself rules over men, and treads down the powers which are contrary to her, and all wickedness.
Or else Christ sleeps, that is, ascends into heaven, where, though He seem to sleep, yet He rises by night, when through temptations He raises us up to the knowledge of Himself; and in the day time, when on account of our prayers, He sets in order our salvation.
Or else, Man casts seed into the ground, when he places a good intention in his heart; and he sleeps, when he already rests in the hope which attends on a good work. But he rises night and day, because he advances amidst prosperity and adversity, though he knows it not, for he is as yet unable to measure his increase, and yet virtue, once conceived, goes on increasing.