Poppies are the origin of medicinal alkaloids such as morphine and have been used for thousands of years as a painkiller
We have 2 types of poppy in the garden:
Opium poppy which has pale green, stemless, frilly leaves.
Common, or field poppies which are low clumps of hairy, fern like leaves
Both varieties of poppy will self-seed unaided, but it is probably best to cast the seed where it is required once the flowers have gone and the seed pod opened. The seeds are tiny, but easily collected. Plants which come up in unwanted spots can be transplanted.