The seeds, leaves, stems, and roots of elderberries contain a cyanide-inducing glycoside, which might make one extremely ill. Take precautions and consult your doctor before taking any of these for medical reasons. Elderberry bushes are poisonous. The elderberry bark might also be poisonous in high amounts – however, it has strong [simple_tooltip text=laxative tooltip=Substances that increase the bulk of the stool and increase bowel movements by loosening it, relieving temporary constipation. ]effects.