A tractor-trailer caravan loaded down with more than a million balsam wreaths is on its way to Arlington National Cemetery.

The “Wreaths Across American” convoy departed Saturday from Columbia Falls, Maine, where the wreaths are made. The caravan will stops at schools, veteran groups, and memorials along the way.

The tradition began when Maine wreath maker Merrill Worcester donated 5,000 wreaths to Arlington Cemetery. Since then, it’s grown each year.

The wreaths are set to arrive on December 15 at the national cemetery, where volunteers will place the greenery on headstones.