Flowers for May Day

Every year on May 1st, my door bell rings and there are two little baskets with flowers on the front porch.  My kids run to the front door and find their special bouquet.
What is special about May 1st?  There is a tradition that on the 1st of May, you give flowers to those you love.  Now, I just pick flowers from my yard and keep it simple, but you can make it whatever you’d like.