My grandfather had potato onions & I would like a start. Is there a veggie exchange where i should post it or does anyone have a source
My memory is far from perfect and I didn't check, but last I knew both Southern Exposure Seed Exchange and Ronniger's carried them, so you might want to check out those two via Google.
You also might want to check out the Allium Forum here at GW and see if they have an exchange area.
There is an exchange area at the Alliums Forum. Plus I would post your request on the forum itself, because more people will see it.
You also might want to check with Horus Botanicals, which carries the largest selection of multiplying onions I'm aware of.
Also, if you're an SSE member, check the yearbook under Onion/Multiplier/Root stareting on page 201.