PORTLAND — Tens of thousands of wreaths destined for hundreds of veterans cemeteries and monuments were set to depart eastern Maine on Sunday to take part in what has been called the world’s largest wreath-laying ceremony.

For the 19th year in a row, wreaths from Worcester Wreath Co. in Harrington will be laid on soldiers’ gravestones next Saturday to pay tribute to the nation’s veterans. A caravan of 20 tractor-trailors will leave Harrington on Sunday, with five of the trucks bound for Arlington National Cemetery.

But the annual event has grown beyond Arlington, Va.

Similar ceremonies will take place at an additional 545 locations in all 50 states and 24 overseas locations with 215,000 more wreaths.

Company President Morrill Worcester began shipping wreaths to Arlington in 1992 when he found himself with 5,000 wreaths extra in mid-December, too late to bring to market. In 2006, he founded Wreaths Across America to coordinate other wreath-laying ceremonies.

He’s been astounded by the growth of the event.

“I couldn’t believe there are as many people around that feel as I do,” said Worcester, who never served in the military.

In all, more than 50 truckloads of wreaths made at Worcester Wreath are making their way to veterans’ graves nationwide. More than 30 of the trucks left earlier this week.

Of the 20 that depart Sunday, five will go to Arlington, where the 24,000 wreaths surpasses the 16,000 provided last year. The rest will veer off from the caravan in Maine for other destinations.

Worcester was asked to provide more wreaths this year for gravestones at Arlington of casualties from Iraq and Afghanistan.

In all, the company is donating about 20,000 wreaths for the ceremonies, with the remaining 195,000 paid for by donations from corporate sponsors, veterans groups, the USO and individuals, Worcester said.

Trucking firms are donating their services to transport the wreaths.

For the 770-mile trip to Arlington, the convoy will be accompanied by members of the Patriot Guard Riders, a national group that strives to recognize veterans. Along the way, it will make 26 stops at a veterans hospital, schools, town squares, parks and other spots, including at the USS Constitution in Boston.