They are technically biennials, not perennials, and will bloom the second year like all biennials. If you don't want them to go to seed and reseed themselves then just harvest and use those. The ones you leave will still continue to divide. If you just pull of the blooms and leave them they begin to die back and the eating quality is lost.

Dave

So basically harvest and plant will still divide? What else affects eating quality? Right now mine are STRONG. I use them very little and occasionally pull some stems to thin them out but not often.

The mildest are the young ones, the newest ones, that are harvested in cooler early summer weather (or late spring in my zone). As they age and the ground and weather gets hotter they get stronger in flavor. And the ones that are in year two and beginning to bolt, to bloom, will be the strongest ones.

And of course different varieties will have different flavors and other growing conditions like soil pH, water, and nutrients can modify flavor somewhat.

But it also depends on how you use them. If you just want to eat as is or chopped in salads etc. you might prefer the younger newer ones for the milder flavor. But even the old guys can be chopped and dehydrated, ground into onion powder, or frozen to use in cooking just like bulbing onions are.

Dave

There are two types of "bunching" ( non bulbing onion) Allium fistolosum which last for years by simply dividing the clusters when necessary and Allium cepa which has the same growth cycle as as its bulbing bothers, Just does not bulb. If you know the name of your variety we can get more specific.

Good point. I assumed the common A. fisto.

Dave

I wish I knew but I planted a few kinds not sure what ended up "sticking"

But Dave, A fistulosum is the perennial one, not biennial.

I realize that some sources refer to fistos as perennials and some treat them as such in certain climates but their growth nature is actually biennial.

Dave

Interesting. I've never seen it referred to as anything other than perennial and that is certainly the view of the RHS. Allium fistulosum

Any favorite A. fistulosum "bunching"? To try to overwinter 6a/5b and divide in spring? Maybe the individual stalks themselves are biennial but some clumps appear to multiple endlessly in good conditions.

Have (I think) 'Nebechan' in the ground from last spring and may survive, I'll find out. Hybrid I think, bought seedlings from a speciality store.

Was thinking of starting seeds of 'Heshiko', a tradition type that from what I read does clump multiply and overwinter, while the common 'Tokyo Long White' does not multiply.