I half expect this to be closed, but in Louise Penny's novels set in and around Quebec, three pine trees are said to have been a sign of sanctuary for British Loyalists fleeing the Anglo-American War. I can find no confirmation of this, and considering how long it would take for the trees to grow, and how short the War actually was, seems unlikely. Is there any truth in this suggestion, or is it merely a fictional device?
This may be more than fictional backstory. From a website concerning genealogy of Loyalist ancestry:
Softwoods also have significance for Loyalist descendants. In the Jan 10 issue of Loyalist Trails, Denis Robitaille, Ph.D, Président de la Société d'histoire Forestière du Québec, tried to verify a familiar anecdote about plantation of white pines and the immigration of the Loyalists into the province of Quebec. He had heard that the inhabitants sensible to the Loyalists cause living close to the U.S. border (Frelighsburg, Saint-Armand, Sutton, Knowlton, Dunham, Bedford, ...) planted three white pines in front of their house to tell Loyalists that they were welcome to their home. To date no reference has surfaced.
This was dated "Loyalist Trails" 2010-17: April 25, 2010, so considering the publication of Still Life, the first of the 'Three Pines' novels appears to have been 2005 it is possible the above 'familiar anecdote' is due to people interested in the novels.
An interview with the author found states the following concerning the three pines legend:
An elderly woman sitting beside Penny at a church supper mentioned that her husband’s ancestors had long ago planted three pine trees on the family homestead as the customary signal to the Loyalists that they were in safe territory. “But then other people from the Townships who have read Still Life say they’ve never heard that story before, so I have no idea if it’s true,” adds Penny. "It’s real imitation folklore."
My father bought a farm just outside of the Town of Brome Lake (Knowlton - which is "Three Pines" in the Penny novels) Quebec, in the Eastern Townships in 1947 - when Louise Penny was barely alive. Our family was very familiar with many descendants of the Loyalists and among them was the knowledge passed down that if there was one White Pine planted in front of a house, that house was a haven for Empire Loyalists. Truth or lore?
Therefore, I would not attribute this 'lore' to Louise Penny.
I live in Dunham and I sometimes notice three pines planted together in prominent locations. Most notably, there are three mature pines at the main crossing in Frelighsburg. They are quite old. I cannot say if the lore pre-dates the books but the trees do. It is a distinctly Loyalist area wedged between the border and the French speaking Saint Lawrence Valley around Montréal.