HALIFAX, NS- For the past 43 years, Nova Scotians have sent one of their biggest and best Christmas trees to Boston by truck to thank their southern friends for the help that Boston provided after the deadly explosion in Halifax in 1917.

And don’t mistake it for an ordinary tree. Here are five things you need to know about the tradition:

1. Dec. 6, 1917: two ships collided in the harbor, causing an explosion that wiped out nearly half the city of Halifax. It left 2,000 people dead and hundreds more injured or homeless.

Boston sent doctors, nurses and medical supplies by train and were the first to arrive, despite delays caused by a blizzard. They were also the last to leave. The tree is a symbol of gratitude for their help.

2. No ordinary tree: each year Nova Scotia sends one of its biggest and best trees, typically sends a red or white spruce or a balsam fir tree between 40 to 50 feet tall, which arrives in Boston on the back of a flatbed truck. This year, Boston will receive a 43-foot white spruce, about 55-years old from John and Ethel Ann MacPherson of Purlbrook, Antigonish County. It’s the first time in the history of the tradition that the tree will come from the northern part of the province.

3. It’s in the delivery: Of course, only the best of truckers can be entrusted with the job. In 2012, the job fell to the late Gerald Hilbert Knol, who lost his battle with cancer in August 2013.

“He was a legend in the trucking world around here,” Gavin Leggate told todaystrucking.com, “known for always getting the toughest of the tough jobs done.”

After serving in the military for two years, Knol broke into the transportation industry transporting everything from generators to Quebec during the ice storm of ’88 to snow blowers to Newfoundland during the heavy storms of 2000 and 2001.

His obituary reads: [He] moved locomotives for the Museum of Industry in Stellarton, an airplane for the NSCC and many other unique jobs. Having fun while earning a living. His proudest moment was transporting Nova Scotia’s gift to Boston, the Christmas Tree for 2012.”

4. Community: Nova Scotia’s community comes together for the selection and takedown of the tree and of course, there’s a ceremony when the tree arrived in Boston too. This year, staff and students from the environmental technologies program at the Nova Scotia Community College Strait Area Campus will cut the tree on the MacPhersons’ property during a public ceremony Monday, Nov. 17, at 10:30 a.m. The province will transport the tree 1,117 kilometres to Boston.

5. Tradition: Atlantic Canada has sent down a tree to Boston every year for the past 43 years in a row. The tradition had lapsed for a few decades between 1918 and 1971, but has since resumed. The province of Nova Scotia is entrusted with delivering the tree each year.

Last year, to pay their respects to the people who died or were injured during the Boston marathon bombings, the Canadians sent a team of three runners out of Halifax to lead the flatbed truck hauling the extra-special Christmas tree.