Papaver Somniferum
Though commonly grown, and widely available as ornaments, poppy-heads contain opium, so that the infusion is bitter, calming, highly analgesic, potentially poisonous and of questionable legality. Poppy tea seems to have been almost an everyday drink in the Fenlands during the 19th Century, and is far from unknown today.
'Poisons - their Effects and Detection' of 1895 has; "The ignorant use of poppy-tea has frequently caused the death of young children; thus in 1875 an inquest was held at Chelsea on the body of a little boy two years and a half old. He had been suffering from whooping-cough and enlargement of the bowels, and poppy-tea was by the advice of a neighbour given to him. Two poppy-heads were used in making a quart of tea, and the boy, after drinking a great portion of it, fell into a deep sleep, and died with all the symptoms of narcotic poisoning." Similar cases are recorded from the late 18th Century to as recently as 2013.