Convallaria majalis, commonly known as the Lily of the Valley, is a poisonous flowering plant found in New Mexico. It was frequently shown in Season 4 of Breaking Bad. When Walter White was contemplating how he was going to topple drug kingpin Gustavo Fring, he noticed the potted lilies in his backyard. ("End Times") Brock Cantillo was poisoned by Walt in an unknown way with the Lily of the Valley berry. The doctors initially thought Brock was poisoned by ricin as Jesse Pinkman had suggested but
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How Poisonous Is Lily of the Valley?(Thought this might be an
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Breaking Bad: How Walt Actually Poisoned Brock
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Breaking Bad: Lily of the Valley Scene
Lily of the Valley, Breaking Bad Wiki