In a large saucepan, cook bacon until crisp; drain. Add potatoes, broth, carrot, onion, parsley, celery seed, salt and pepper. Cover and simmer until potatoes are tender, about 15 minutes.
Combine flour and milk until smooth; add to soup. Bring to boil; boil and stir for 2 minutes. Add cheese, stir until cheese is melted and the soup is heated through. Garnish with green onions if desired.