A 15-metre tree from Nova Scotia is on its way to Boston as part of an international Christmas tradition that has been going on for almost 40 years.

This 15-metre tree will be erected in the Boston Common on Dec. 2. (CBC)

The province has sent a tree to Boston every Christmas season since 1971 to thank people in that city for their help in the aftermath of the devastating 1917 explosion in Halifax.

The white spruce from the Annapolis Valley was on the road Tuesday, and the tree will be raised in the Boston Common Dec. 2.

The present was wrapped for the occasion, with its boughs tied up to protect them on the road trip. About 160 schoolchildren attended the 10 a.m. cutting, and author Bruce Nunn read from Buddy the Bluenose Reindeer and The Boston Christmas Tree Adventure.

The 50-year-old tree was on Gary Misner's property in North Alton, and he offered it to the province when it got so big he was worried it might topple onto his house.

Tree becomes Boston focal point

The tree usually comes from a private landowner and is selected by the Nova Scotia Department of Natural Resources. It must be 12 to 15 metres high, healthy and have good colour.

The tree is transported to Boston by the province. Once erected, the tree is decorated with thousands of lights and becomes the focal point of the city's annual tree-lighting ceremony.

In 1917, the Norwegian supply ship Imo collided in Halifax harbour with the French munitions ship Mont-Blanc, which was carrying so much TNT that, at precisely 9:04:35 a.m. on Dec. 6, the largest man-made explosion the world had ever seen destroyed more than 1,600 homes and killed almost 2,000 people.

On the night of the explosion, the city of Boston prepared two trains filled with medical supplies, equipment for a 500-bed hospital as well as doctors and nurses. The Boston Symphony also held a benefit concert 10 days after the explosion to raise funds for the relief effort.

The tree's journey to Boston can be followed through the Twitter account novascotialife.