According to ProFlowers, the birth flower for a January birthday is a carnation, an iris for February, a daffodil for March, a daisy for April, a lily for May, and a rose for June. In addition, the birth flower for July is a larkspur, a gladiolus for August, an aster for September, a marigold for October, a chrysanthemum for November and a poinsettia for December. Birth flowers are generally in bloom or readily available from florists around the month in which one celebrates one's birthday.
Birth flowers are not universally standardized, so there are some variations and alternate flowers. These include snowdrops for January, primroses for February, jonquils for March, sweet peas for April, lily of the valley or hawthorn for May, honeysuckle for June, water lilies for July, poppies for August, morning glories for September, cosmos for October and narcissus or holly for December.