My father loved to read old English nursery rhymes to us children when I was small, so May Day always reminds me of the verse:
The fair maid who, the first of May,
goes to the fields at break of day
and washes in dew from the hawthorn tree
shall ever after handsome be.
I have no idea what a hawthorn tree looks like (well, yes I do-- I just looked it up on Google) but I do know what lilies-of-the-valley look like. And they smell lovely too. As I was walking into my building yesterday, our wonderful concierge/gardienne , who was standing outside her loge talking to a friend, stopped me and told me to wait a second. She popped inside and brought out a little bouquet of muguet des bois for May Day from her country house. (Yes, our gardienne has a country house! People are paid correctement in France. She also has six weeks vacation a year, a pension and excellent health care, and the loge with its two bedrooms is rent-free. Her salary is not very high but her husband also has a good job.)
I don't know where the tradition of lilies-of-the-valley on May Day came from in France. May Day is also Labor Day/la Fête du travail here; unfortunately it was drizzling and miserable most of the day and I was glad I didn't have outdoor plans, like these poor marchers. But anyway, it's the one day of the year when anyone is legally allowed to sell lilies-of-the-valley on the street, as you can see above.
But don't try to eat the flowers! They're poisonous. I wonder who found that out.