Why is tonight's full Moon called the Flower Moon?

Tonight's full Moon is called Flower Moon. The Maine Farmers' Almanac began publishing 'Indian' names for full Moons in 1930s and these names are now widely used. According to this almanac, Algonquin tribes of what's now north-eastern US called May's full Moon Flower Moon for the flowers that are abundant this time of year. It's also called the Corn Moon.