In Canada, the annual Tulip Festival is held in the national capital of Ottawa, Ontario.
It started with a gift in autumn 1945 from Princess Juliana of the Netherlands. She presented the city of Ottawa with 100,000 tulip bulbs. This gift was provided as a token of appreciation after World War II.
During the war, Holland's royal family was exiled to England. During the darkest days of the war for the allies, when England itself was in peril, Queen Wilhelmina sent Princess Juliana and her two young daughters to Canada. They received safe haven in Canada's Government House in Ottawa. During this time, Princess Juliana's third child, Princess Margariet, was born at the Ottawa Civic Hospital. (Dutch law required that any heir to the throne must be born on Dutch soil, so Canada'a parliament declared the hospital room where the baby was born to be the territory of the Netherlands for the duration of the delivery!)
The gift also recognized that Canadian troops were the primary Allied forces that liberated the Netherlands from occupying Nazi troops at the end of the war. The Dutch people were starving, with most of their meagre food and supplies stolen by the German forces.
Each year since 1945, 20,000 additional bulbs have been sent to Canada as a gift - half from the royal family, and half from the Associated Bulb Growers of Holland. The May festival has now become into the largest tulip festival in the world, with over 3 million tulip blossoms annually in the National Capital Region.
More info on the Canadian role in the liberation of Holland can be found at:
http://www.magma.ca/~louievb/liberation-war/sig-paper.html
The Tulip Festival's home page is http://www.tulipfestival.ca, and an excellent article is found at:
http://www.legionmagazine.com/features/celebratingcanada/99-05.asp