Do not pull up the weeds, for if you do, you might end up uprooting the wheat along with the weeds. Let them grow together until harvest when it will be easier to gather and burn the weeds without harming the wheat. The parable of the weeds in the field (also known as the parable of the darnel) is one of those parables that are meant to challenge our understanding of the kingdom inaugurated by Jesus. Most of us would think of the kingdom of God as an exclusive club, a preserve for a pre-selected few, a club where once an individual gets kicked out, he/she should never be allowed back. It is highly likely that among the many challenges that the early Church had to face, one of them was how to deal with members who had sinned or who were grappling with infidelity in living their Christian call. Such individuals must have been perceived as a disgrace to the faith and the sooner they were gotten rid of, the better it was for the Church. This scenario must have played out more explicitly in the community to whom the Gospel according to Matthew was initially addressed (generally known as Matthean community). 
Members of the Matthean community were majorly of Jewish background. As such, their concern was not only seeing in Jesus a fulfillment of the hopes of the Old Testament both in the larger and minute details, but also a continuation of Jewish customs and ways of thought. One such custom was the exclaustration of individuals who had committed sin (cf. Leviticus 18:29; Numbers 15:30, 19:20; Ezra 10:8). But such practices were proving incompatible with the teachings of Jesus. Today’s Gospel parable about the weeds in the field seems to have been directed to address such situations.
To rightly interpret the parable, we must understand it from the perspective of the sower (owner of the garden). And as with the parable of the sower (cf. Matthew 13:1-23), we might also be tempted to focus too much on either the wheat or the weeds and forget about the owner of the field (the sower). I tend to believe it is what the owner of the field suggests that is the focal point of the parable. “ Let them grow together until harvest,” he tells the workers. The sower was concerned neither with the weeds nor with the appearance of the garden. Sure, he must have wanted the garden to look smart. He must also have wanted everything to be just perfect so that he could maximize the yield. This would have included uprooting all the weeds from the garden. But he also knew the risk that was involved in trying to uproot the weeds. The roots of the weeds were already intertwined with those of the wheat and any decision to uproot the weeds would have disastrous consequences for the wheat. Moreover, at that particular stage of growth, it was almost impossible to distinguish the wheat from the weeds. Because of his concern for the wheat (he was not concerned about the weeds), the sower decides to let both the wheat and weeds grow together until harvest time when it would be easier to tell them apart. Although the field would become an eyesore, the sower was going to wait. He was going to be patient.  
The parable speaks about God’s relationship with us. God’s relationship with us is characterized by patience, clemency, kindness, and leniency on the side of God (God’s justice). God is never in a hurry to sentence us even if our conduct would warrant it. As the Psalmist has rightly put it, if God were to count our iniquities, no one would stand worthy of God’s presence (cf. Psalm 130:3). God will always give us time hoping that we will change our ways and turn to him. God waits until the end. And so should we with those we consider "weeds" in our midst, those who bring us discomfort.