All parts of which plant are highly toxic?

Lily of the valley is known for being highly toxic, with all parts of the plant containing toxic compounds, especially cardiac glycosides. These substances can cause serious heart disturbances and other systemic effects when ingested, making even small amounts very dangerous. This plant's toxicity is well-documented, and exposure can lead to symptoms such as nausea, vomiting, and potentially fatal heart arrhythmias.

In contrast, while Jack-in-the-pulpit can be irritating if ingested, it does not have the same level of systemic toxicity as Lily of the valley. Poison ivy primarily causes skin irritation through its oil, urushiol, and while it can lead to an allergic reaction, it is not harmful if merely touched or handled without direct contact with the oil. Golden rod is generally considered non-toxic and is often used in herbal remedies, where it is not associated with any significant toxicity.