Convallaria majalis, commonly known as the Lily of the Valley, is a poisonous flowering plant found in New Mexico.
Brock Cantillo was poisoned by Walt in an unknown way with the Lily of the Valley berry. The doctors initially thought he was poisoned by ricin as Jesse had suggested but later discovered the true toxin. The doctors and Jesse believed that Brock came across the flower growing naturally and ate some poisonous berries. ("Face Off")
After returning home from successfully killing Gus and getting Jesse back on his side, Walt disposed of the Lily plant from his backyard. ("Live Free or Die")
- Lily of the Valley at Wikipedia