UC Master Gardener Francie Murphy was pruning the succulents in her San Diego front yard when an unfortunate accident catalyzed her commitment to communicating the dangers of toxic plants. She trimmed a stem on her drought-tolerant pencil milk bush and milky sap spurted into one eye, causing stinging pain.

“I tried to wipe it out, and in doing so got in both eyes. I was blinded. The pain was unbelievable,” she said.

A nearby friend rushed her to the emergency room where the doctor diagnosed chemical burns to her corneas and washed her eyes with two liters of saline water each. Murphy removed the plant from her garden, but saw it growing throughout her...