Plant a Scallion in Sunsong Ranch. You can purchase seeds from Merchant Greenfield in the Halfhill Market.
Plant Scallion Seeds
I heard Haohan mentioning that he was going to plant scallions today. I'm not sure if today's the best day for scallions, but I'd like to hope that he knows what he's doing. He is the head of the Tillers' union, after all.