The previous parable as well this one: But he that received seed into the good ground is he that heareth the word, and understandeth it; which also beareth fruit, and bringeth forth, some an hundredfold, some sixty, some thirty. (Mt 13:23)...But when the blade was sprung up, and brought forth fruit, then appeared the tares also. (Mt 13:26)
What is "the Word" and who bear fruit after hearing that Word? The Word is the Gospel and only those who believe on the Lord Jesus Christ bear spiritual fruit. The tares are the fake wheat.