Somebody in the bay area earlier today on FaceBook asked about Egyptian Multiplier/Tree Onions....here is what I've experienced, read about to date. There are MANY MANY kinds, including a whole subgroup called Cattawissas (sp?). WhatEVER kind I grew in Denver that multiplied like CRAZY in my garden and clients' gardens, it failed after just a few months each time I tried it in my Tampa garden....THICK white stalks, truly "walking" viviparous stalks with bulbils at the end, flavor like a GIANT scallion but in massive clumps...the leaves had great flavor too. In Denver it was almost invasive. About 5 years ago Allen Boatman and I obsessed on Egyptian Multipliers for the Tampa Bay area....gene studies say they all originated a LONG time ago from a cross of regular onions (Allium cepa) and another species (fistulosum?)...I think they call it Allium proliferum (?). Allen got a strain that for three years THRIVED here for him, me and two other gardeners....as we entered year four they all went into a sudden decline then died. Might be fun to try to track down ones from and FOR subtropical regions. The Allium family is very diverse and a little confusing, but since I literally can't cook without onions and garlic, I'll keep obsessing!