I have not grown Guardsman, but other varieties bunch twice a year -- once in spring and once in fall. Right now I have some spring-planted bunchers in full division mode, multiplying into 4 plants each. They look like they will keep multiplying for a while. I like to lift the clumps, harvest lots of onions, and replant the individuals that get through the process with the most roots. Lifting and moving the clumps helps prevent problems with onion root maggots in my climate.

I'm not familiar with Guardsman either, but allium fistulosum - aka green onions, welsh bunching, japanese bunching, negi, etc - are one of my real favorites because they are:

1) easy to grow
2) relatively pest free
3) productive
4) perennial in my climate (and surely Bay Area as well)
5) propagate themselves
6) tasty & versatile in the kitchen
7) good for you
8) can be continuously harvested as cut-and-come again crops
9) easy to grow in containers or garden beds

10. can be grown from the bottoms of storebought produce

As mentioned, they will divide themselves once or twice a year. I love the way they look as they look like kids wiggling out of their clothes - see attached pic.

They will also flower and reseed themselves... or you can gather seed to start a new bunch elsewhere in the garden. As with most allium seeds, the seed doesn't store very well. If I gather seed, I replant within a month or two, if not immediately. They germinate quickly.

We have 2 types, both grown from the bottoms 1/2 inch bottoms cut off of supermarket produce. One is the common 'green onion' type sold in supermarkets. The other is a larger Japanese type, also storebought from a Japanese market. We like the larger ones better, as they have more of that sweet, oniony 'umami' taste. We only have 4 of the bigger plants (up from 2 a month ago) and would like to have more of the large Japanese types. Just planted some old 'Tokyo Long' seed, I am hoping is still viable and some 'Welsh Bunching' I picked up at a seed swap. We'll see what I get from those.

The larger varieties of allium fistulosum is often 'hilled up' by various methods to blanch the stems. The Japanese will bury the shaft of their big ones a couple of feet, as the white part melts so nicely in soup.

We harvest the outer green leaves almost every day for use in miso soup, salads and other dishes. As we get more of the larger types established, I'll start blanching and using the stems and replant the bottoms.

OH - wait, guardsman is allium cepa, ignore everything I just said. I know nothing about them.

I read you can separate clumps of bunching onions or 'true scallions' and propagate from these clumps. (Though, I'm not sure what a clump is exactly: a huge clump of dirt with roots, or lots and lots of scallions attached to a big ball of dirt?).

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A "clump" in growing something from seeds , happens when a whole bunch of them germinate/grow very close together.
Depending on what they are, you might be able to separate them and plant them at proper spacing. But , for example, you cannot do this with radishes. Because the grow long tap roots that don't like to be disturbed.
Clump here DOES NOT mean any propagation, in any way. Each seedling is grown from a single seed.

ONION family (any thing in alliums family) are the MOST transplant friendly seedlings that you can find.

Simply water them real well ahead of time.
Take them out of pot/cell and place them in a dish of water.
Slightly shaking, take the clumps apart(separate them)

Once they are separated, plant them at proper spacing anywhere you want. Make sure to water them after re-planting. If you cannot finish planting today, keep them in water, (in cool shaded) and plant them tomorrow.

P.S.
I have a flat of bunching onions that I want eventually plant in the garden. I have started transplanting the to nursery pots. I did 4 pots (each about 10) the other day. I will continue doing that.
Once the seedling are strong, I will re transplant them into garden for fall/winter use.
Let me tell you: It is very hard to kill an onion seedling during transplant.

This post was edited by seysonn on Mon, Aug 19, 13 at 6:41