Genesis 1:11 - The Yielding Seed

And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.

God created the seed within itself to grow and multiply. So the farmer tills the ground and plants the seed, the rains fall and feeds the ground; however, the amount of fruit the seed yields, is ultimately determined by God's blessing (Hebrews 6:7). As in the parable, The Sower, some seed died, and some increased at multiple rates, from ten times to even 100 times (Matthew 13, Mark 4, Luke 8).