Are пырей and перо somehow connected?
Some material from PIE:
pulos a single hair of the human body
poums body hair
peumos adult (having hair)
peuqs tail (> Eng. fox)
putos vulva (> Eng. pussy)
I wonder cannot the peuros for wheat derive from "hair"? The proposed derivation by Quassnoi from "fire" looks unlikely to me because the word for bonfire would be pea̯ur, having another root (am I wrong?).
On the other hand, even if Eng. feather is traditionally derived from peta̯trom (a root meaning "fly"), why it cannot be derived from something like peutrom? The etymology of перо according to Vasmer is uncertain, but why it could not also derive from peutrom or hypothetic peuros/peurom? If so, then it directly coincides with the word for wheat.