Bract
A leaf that sits just below a flower or flower cluster, sometimes coloured and mistaken for a petal.
A bract is a modified leaf attached where a flower or a cluster of flowers meets the stem. Many are small and green. Some are large and bright and do the work of petals. The red 'petals' of a poinsettia are bracts, and the real flowers are the small yellow beads at the centre. The papery pink, purple or orange parts of bougainvillea are bracts too, as are the four white 'petals' of a flowering dogwood.