If you want the largest bulbs possible, don't clip any green. If you want green onion then harvest them early. If you want to maximize space utilization then plant them as close together as you wish since bulb size doesn't matter to you for these. You can always take any planting and designate a number of them for clipping greens as needed and pulling for green onions when desired.

The bunching onions, which are Allium fistulosum, are the only true perennial onion. This group is commonly known as Welsh onions (not because they are from Wales, by the way, but from the German word 'welsch' meaning foreign), Japanese bunching onions, bunching onions, long green onions, spring onions and scallions. However, people often refer to some non-bunching onions by some of those same names (especially scallions) so it can get confusing. The other onions commonly referred to as perennial onions are Allium cepa var. aggregatum and are not true perennials but act like perennials. How's that for confusing? This includes all the multiplier onions, also variously referred to as walking onions, Egyptian onions, potato onions (nothing potato-like about them). There is no true perennial onion that produces huge bulbs like the biennial onions that we all plant in winter and harvest in late Spring and early Summer. If you like the Allium fistulosum type of onions and want to try others that are not as well-known as Japanese Bunching, Evergreen, Tokyo, etc., then the Oriental seed company based in California, Kitazawa Seeds, offers 8 different varieties of them: Seeds of Bunching Onion Varieties From Kitazawa Seed In some soils the perennial onions may not be perennial. They can have a hard time surviving prolonged excessively wet weather in clay soil, so do best in raised beds with well-drained soil, including very well-amended clay.

Too bad it costs me $20 in gas for the roundtrip. I got a dozen of so loads from the old site back when gas was cheap and I worked in the area. Now it's just too far.

try this : cut the green top off, save about 4 inches of the bottom measure from above the roots, do not cut the roots off yet, place the 4 inch stalks on a paper towel for ,3-4 days to dry out the roots a little. get a pot of damp not wet soil 6-8 inch pot is good for about 6 stalks. after 3-4 days trim the long shriveled roots to about 1 inch,poke a hole and place one stalk in each hole and press soil around the stalk place near a bright window keep soil a little damp, in a less than a week you should see the top of the stalks start to raise up and grow,i normally can cut green leaves about a month later. i have used this method since i was a child (i am 65 yrs old)my mother did too.the only time i purchase green onions is if i use up all from my garden.another tip to try: after you cut your green tops off wrap the green tops in a dry, yes dry paper towel then a sheet of dry newspaper and store in refrigerator,no plastic, this method cuts down on slime and the green tops last a little longer,