Is it ensure, insure, or assure?
One of the usually separate, green parts that surround and protect the flower bud and extend from the base of a flower after it has opened. Sepals tend to occur in the same number as the petals and to be centered over the petal divisions. In some species sepals are colored like petals, and they can even be indistinguishable from petals, as in the lilies (in what are called tepals). In some groups, such as the poppies, the sepals fall off after the flower bud opens. See more at flower.