I was told of an area, not too far from my home, with large numbers of flowering Heliotropium weeds (family Boraginaceae) and wanted to find out how long I could expect the flowering to last. In the process of collecting information about the plant, I was stunned to learn that, not only is the plant poisonous ("tea" made from leaf infusions has caused deaths), but the nectar contains poisonous alkaloids. It wasn't stated quite definitely, but the implications were clear that the honey could also be poisonous.
Does anyone have any first hand information about this, or of any other common plant source that might produce poisonous honey?