Identifying a Plant with Coin-shaped Translucent 'Petals': Eucalyptus or Lunaria?

Reader describes a plant with twig stems and nickel/quarter-sized milky translucent 'petals', thought to be Silver Dollar. Expert Darlene: if a tree, likely eucalyptus; if a plant, Lunaria annua (honesty). Both are outdoor plants—eucalyptus needs bright light, Lunaria needs winter freeze. Suggests Google images and seed sources.