Any broken part of milkweeds wards off herbivores via a poisonous latex that it exudes.

References

"Milkweed gets its name from a poisonous latex that exudes from its broken stem. This is so toxic that it can give a small animal a heart attack." (Attenborough 1995:70-71)

Book
The Private Life of PlantsBBC BooksMay 27, 2017
David Attenborough

Living System/s

Organism
Asclepias