What are the worst herbs in warrior cat series?

In the "Warriors" series by Erin Hunter, some of the least favored herbs include Deathberries, which are toxic and can be lethal if ingested. Other undesirable herbs include Foxglove and Hemlock, both of which are poisonous and can cause severe harm to cats. While not traditionally "worst" in terms of effectiveness, these herbs pose significant dangers to the cats in the series, emphasizing the importance of knowledge in herbal medicine.