Start the water boiling while preparing the vegetables. About another half hour after all the veggies are happily cooking together, it should be ready. Although it's not absolutely necessary, for crisper texture, you can add the green onion maybe 5 minutes before the end.
Actually flat-leaved parsley goes well in place of the green onion, but I was out the day I prepared a batch and typed in this recipe. But it came out quite good with the green onion.
So use green onion, parsley, or both!