Lily of the Valley especially for my French friends -- Vagabonde, Therese, and Miss Yves. (I'm told that sending lily of the valley on May Day is traditional in France.)
Once it was the custom to leave a basket of flowers hanging from your neighbor's door knob (see HERE) -- a charming tradition that has pretty much gone now -- along with the Maypole.
So consider these blossoms your virtual May basket.
You'll have to imagine the Maypole. Or watch THIS.
Also, my maternal grandmother always said that getting wet in the first rain of May would ensure good health in the coming year. She lived to 91. I've already gotten my dose of good health -- it was raining lightly when I went out to fill the bird feeder.