Some plants absorb excess nitrates or oxalates from the soil and store them in plant tissues. Toxicity problems can occur in animals which feed on these plants.
Rooting tonics contain plant growth hormones used to stimulate root growth during plant propagation. They're easy to make at home.
Poison oak plants contain a chemical that causes a severe rash. Learn how to spot a plant, safely remove, and clean your clothes, gear and skin afterward to prevent a rash.