This refers to the young plants. This may be stated in active form. AT: "it scorched the young plants" (See: [[rc://en/ta/man/translate/figs-activepassive]])
All of the seeds that the farmer sowed are spoken of here as if they are one seed. See how you translated this in [Mark 4:3](../04/03.md). "Other seeds ... choked them ... they did not produce"