Hi Again Until you sent this I have never noticed the keel on the underside of what I am growing as A. neapolitanum. But it is present, just not as noticable. They are just that different when you have them in the same garden. In flower they are quite different, out of flower in my garden A. triquetrum is robust and at a glance could be mistaken by its general appearance for an untidy vigorous snowdrop, as it is quite glaucous, whereas my A. neapolitanum, if that is what I am growing, is floppy and much greener, with only some glaucous colouring on the upper surfaces. I currently have A. paradoxum, var. normale in flower. Brian Whyer, Buckinghamshire, England, zone ~8 --- On Sun, 4/4/10, David Ehrlich <idavide@sbcglobal.net> wrote: > Hi Nhu, > > The problem is that Allium neapolitanum also has a > 3-sided peduncle with white flowers and is also common in > the Bay Area. I think the best indicator is that A. > neapolitanum has erect flowers while those of A. triquetrum > are drooping. I have also read that the peduncle of A. > neapolitanum may be slightly winged on two of its angles. > > Thanks to all of you who answered. The reason I asked > this question is that one (or both) of these onions is a > common, though not particularly aggressive weed in my > neighborhood, and I wanted to know which species it is. > Keying it out in two different keys gave me the two > different answers.