the 'tares' put forth black buds or ends making them easy to recognize. This is horticulture, not heresy.

Matt 13:27   So the servants of the householder came and said unto him, 'Sir, didst not thou sow good seed in thy field? from whence then hath it tares?'
28    He said unto them, 'An enemy hath done this.' The servants said unto him, 'Wilt thou then that we go and gather them up?'
29    But he said, 'Nay; lest while ye gather up the tares, ye root up also the wheat with them.

    It's difficult to really point out one of these children of Satan ('tares'), because one of God's own could be doing evil things by following Satan,

 

 Christ is really telling us here, to leave them alone. In other words, hold to His Word and Law. You don't have to put up with evil right in your back garden. But don't go out in the world like a vigilante seeking these children out, for you might mistakenly get the good wheat that the tares are mixed in with.
     God said to have faith in Him, that He would never leave or desert us; plus He gave His children power over the 'enemy' (Luke 10). The Word is written, and that's how everything will happen. If you don't like this idea because it may sound too confining for your 'personal' sense of freedom, equality, liberty, and fraternity, then take it up with our Father Jehovah, and maybe He can help you with it.

 

30    Let both grow together until the harvest: and in the time of harvest I will say to the reapers, 'Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.''"

     Now let's turn to Matthew 13:36 and listen to Jesus explaining this parable:

Matt 13:36     Then Jesus sent the multitude away, and went into the house: and His disciples came unto Him, saying, "Declare unto us the parable of the tares of the field."
37    He answered and said unto them, "He that soweth the good seed is the Son of man;

     This word 'seed' here is 'sperma' in the Greek by the way, as it is also back in Matt.13:24 (Strong's no.4690). Who sowed the 'good seed'? The 'Son of Man’ is another name for Jesus

 

 John 8:28: Then said Jesus unto them, when ye have lifted up the Son of man, then shall ye know that I am he, and that I do nothing of myself; but as my father has taught me,  speak these things.

Matt 13:38. The field is the world; the good seed are the children of the kingdom; but the tares are the children of the wicked one;

     The 'good seed' are God's children, those of bloodline Israel which accept Christ, and all those Gentile, and even some of Satan's own (Kenites) who turn away from him and believe on Christ as Saviour.

 The chosen bloodline 'Seed' is according to the election of birth; the latter is according to the election of grace.

 

 See Romans; Chapters 1 - 16 and read all.

 

8:  1 They that are in Christ, and live according to the Spirit, are free from condemnation. 5, 13 What harm cometh of the flesh, 6, 14 and what good of the Spirit:  17 and what of being God’s child, 19 whose glorious deliverance all things long for, 29 was beforehand decreed from God,  38 What can sever us from his love?