During 2016 I purchased some Top, Topset, Top Setting, Air, Tree or Egyptian Walking Onions, during 2017, 2018 & 2019 I was on top of growing the Catawissa onions I had invested in and had 100's of them growing in the space saver greenhouse.
A = Moritz Egyptian
Similar to the typical tree onion, but the bulbs are a deeper colour (red-purple) and the topsets are slightly larger than most strains. An unusual strain that will sometimes produce sets in the middle of the stalk.
B = Catawissa' 'Catawissa Onion'
A very hardy cultivar of Canadian origin, distinguished by its vigorous growth and the rapidity with which the bulbils that commence to grow without being detached from the top of the stem. The bulbils divide into tiers, the second set of bulbils producing green shoots, leaves or barren stems to bring the height of the plant to over 75cm.
C = McCullar's White Topset
This form produces a number of white bulbs below the ground about 2.5cm or more in diameter, plus pea-sized bulbils at the top of the flower stalk. The larger bulbs are used for eating; the bulbils are used for replanting. It is used primarily as a source of greens when other onions are dormant.
D = Amish walking onions
Similar to the Catawissa tree onion, but the bulbs are smaller in size and darker red/purple colour and the topsets are smaller than most strains.
When the bulbils arrive I will post some photos of what I have received, and blog about their progress.