Tulip bulbs have actually never been purposefully regarded as a food item until World War II, when during the winter of 1944-1945, the Netherlands were forced by the nazis into the Hunger Winter.
Considering the rapidly depleting food resources of the country, the bulb stocks came up as a saving solution. It turned out, that the lack of manpower made it impossible for the flower growers to plant their bulbs in the autumn, and while the hyacinth and lily bulbs proved to be highly toxic, the tulip bulbs, on the contrary, proved to be quite comestible, if prepared properly, so the tulip bulb stocks helped the country out of famine.
The Dutch government published a guide on how to prepare tulip bulbs correctly, instructing people to first cut them in half and remove their flower germs, which accumulate toxins. The guide contained as well various recipes of soups, porridge, fried, roasted or mashed tulip bulbs and even ways of making flour from tulip bulbs, for baking bread.
Hard times are luckily long behind, but the tulip bulb has preserved its status of food item. Modern cuisine has explored an reinvented the tulip bulb as a culinary treat, which can nowadays be found on the menu of luxury restaurants.