The word 'tares' in the parable of the wheat and tares, is a translation of the Greek word zizania. This word does not appear in the writings of any classical Greek writers and it is supposed that it was a Palestinian local name for the plant that today is known in the land as ziwan. This plant is definitely poisonous. Travellers have observed that it has the property of causing giddiness and even unconsciousness and that its effect is insidious and often unnoticed until too late. At least one case is on record where a whole community of people was affected by eating ziwan that had not been cleansed out of the wheat that had been used to make their bread. Jesus used an apt simile for his parable.
Parable and Apolpgues
An apologue (or aplogue) is a fable or parabolic tale, with a moral truth; animals, trees, etc., are used as characters, and as it progresses towards the end, the moral lesson can be deduced. A celebrated aplogue is that of the trees called upon to choose a king in Judges 9. The aplogue is in verses 8-15 and the moral in verses 55-57 though the whole chapter is a framework for the subject.
A parable is different, in that it is in itself a pictorial narrative, with a cryptic meaning not so easily understood without a key to the cypher. After His series of word-pictures Jesus privately explained them to His disciples, as is evident from Matthew 13.10,11,16,51 and 52.