Murder by Yew — Suzanne Young

When her handyman dies of taxine poisoning, Edna Davies, amateur herbalist, becomes the prime suspect. Nearly certain that she hadn't concocted a poisonous potion and desperate to save herself from arrest, Edna taps into strengths she never before realized she possessed. Shunned by the townsfolk, questioned by the police, and threatened by thieves, she follows the clues of a forty-year-old disappearance to capture a killer.