poppy seed, tiny dried seed of the opium poppy, used as food, food flavouring, and the source of poppy-seed oil. Poppy seeds have no narcotic properties, because the fluid contained in the bud that becomes opium is present only before the seeds are fully formed. The plant, Papaver somniferum, is an herbaceous annual native to Greece and the Orient. Poppy seed is an ancient spice; the seed capsules have been found in Switzerland in the remains of prehistoric lake dwellings.