MY GOD MAN you need to get that out of your garden as fast as you can.
It is called a Bicumtus Serumtus and is the result of an extra terrestrial dumping hazardous waste on your garden.
this happens all of the time in New Mexico out near Roswell.
What I think it really may be is the onion putting on new onions at the top of the mother plant sort of.
the reason I say this is because Agave do something similar on their blossom shoots.
They will shoot up and at some places they put on flowers and others they put out new pups way up in the air.
Supposedly the shoot dies, falls over new seeds sprout and the pups take root.
This is a WILD guess.
The UFO story is about as good.
Worth