Antipodean Bucket Farmer said:

Hi, Everybody,

Like the "Subject" says... How do I tell when my white
onions are ready to eat? Thickness or colour of the
leaves poking out? Or do I need to peek under the soil
a bit? Or, what?

They are edible as green onions or fresh bulbing onions anytime. No need to
wait for the tops to fall over and dry to pick onions for immediate use. (That's
what you will have to do to harvest them for storage, though.) Normally as onions
mature, they bulb will begin to project above the soil.

--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)