Alhough there are over one hundred different types of beans growing in tropical regions all over the world, commercially-available vanilla comes from only three sources: Bourbon-Madagascar, Mexican, and Tahitian pods. Each of the varieties has its own characteristic flavor and appearance, though soil, climate, and curing methods can all affect the bean’s character. The Bourbon-Madagascar beans, which account for about three-quarters of the world’s vanilla bean crop, are thin, rich, and sweet, with a thick, oily skin. The wider Mexican bean is somewhat more rare. These beans have a smooth, mellow flavor, but must be purchased with some care and from reliable sources since some Mexican vanilla products have been found to contain an FDA-banned toxin, coumarin. Tahitian vanilla beans, the shortest, plumpest, and darkest of the three, are extremely aromatic, but somewhat less flavorful. These pods also tend to contain fewer seeds.