I personaly relate red common poppy with the right of passage between worlds .To me it is the flower of the dead especially those who had fallen into battle .
It has a lot to do with the cycle of life ,death and fertility hence its connection with Persephone .
Opium poppy has to do also a lot with dreaming and reaching alterate states of mind it sorts of helps this right of pasage ,however i will not recommand ingesting opium poppy seeds !Poppy and Mandrake often were present into druids medicine bags .
Poppies used to appear within the corn whenever fallen soldgers and army had fallen and destroyed the crops ,memorizing this moment with their red color .Interesting about them is that they can be gone years and they can return again out of nowhere and then vanish again as if they had died off ,but then they are reborn .
I would put poppies on the Goddess side of the altar to symbolizes her fertility and resistance and i would put them also on ancestor altar in memory of my beloved ancestors and as symbol of the fact that i have never forgotten them and they are in my blood and in my memory and heart .
By the way you did not mention what type of poppy that is if its common you can eat also the seeds they are mild sedative and they are nutricious ,also use them as fertility charm .
Also some people collect the flower heads before they open bruise them and let them soak in wine(few weeks at least ) .The wine then is drink before you go to sleep .
When we were kids we would make sort of doll from this flowering heads i think it will be good one for mojo bag that has to do with fertility ,after all soul released from old body is soul that later on is brought to new .:)