The Greek word, Zizanion, in the earliest texts is translated tare , and it is not just any ordinary weed. The Zizanion is the bearded darnel, a particular grass that is almost indistinguishable from wheat while the two are in the blade stage. But, when the plants mature, their ears are quite different. The fruit of the darnel or tare is more colorful than the wheat and has a bit of a flower that the wheat does not. And there is another, more lethal difference.
Wheat produces a basic food staple, and darnel produces a deadly poison.
Jesus is simply telling you to be the spirit of God in a sinful and deadly world. He is assuring you that you do not need to be a super man, super woman, or super Christian. Jesus wants you to BE wheat. He is warning you that if you choose to be a weed, you will have made a deadly and a dangerous choice. But, in this story, Jesus also acknowledges the mystery of wickedness.