Hi
I bought some onions a couple years ago end of season labeled only "bunching onions." I decided I would just treat them as perennials. Now the plant is 2' tall and some of the leaves (scallions?) are more than 2" thick. I've collected the seeds but have never planted them.

I've tried unsuccessfully to research what kind of onion I have, or whether this is just what happens to a scallion-type onion when you leave it in the ground forever.

It's definitely some kind of fistulosum because it's got a big hollow leaf.

Any of your thoughts on the matter would be of interest to me. Thanks!

My Egyptian Walking onions do not flower like that. Mine set onion sets that fall over and root to start a new plant. Those actually just look more like a normal onion.

Hollow stems are normal for their size and age. Several types are bunching onions, Welsh onions, scallions, Japanese bunching onions, green onions, spring onions - all the same. A perennial non bulbing allium like you find in the grocery store, not sure if there is a specific name for them, just the common ones above.

Thank you! Great answers. I haven't yet cooked these giant scallions. Would you just treat them the same as normal narrow scallions recipe-wise?

I would, at least until you know what flavor profiles they have that might not be quite what you were expecting. Soil ph can affect allium flavors....