Preheat oven to 375°F.
Remove leaves from tea bags. Put green tea leaves, celery, salt and pepper inside the duck cavity. Truss the bird. Prick the duck’s skin with a fork in several places to render duck fat as the bird steams. Pour boiling water into a roasting pan with a tight fitting lid and rack. Stir in green tea powder. Place roasting pan on large burner. Put the duck on the rack, cover, and steam over medium heat for 2 to 2 1/4 hours. It should be tender when done but not falling apart. Check every half hour that the water level remains just below rack. Top up with water if necessary.
Mix glaze ingredients together in a small bowl. Remove lid from roasting pan. Brush duck with glaze. Roast duck in oven, basting every 20 minutes for 45 to 60 minutes. Serve with steamed bok choy and steamed kumquats.