In Gryfino, western Poland, there is a forest containing an unusual mystery. Around 400 trees – surrounded by trees growing normally – are bent 90 degrees at their base, with the majority of them bending towards the North.

We know that the trees were planted some time in the 1930s, before Gryfino was invaded and destroyed in World War II, with residents abandoning the town and taking with them clues to what deformed these pines.

There are, however, a number of theories about how the trees got misshapen. Of course, there are people who believe the trees were crushed by an alien spacecraft, perhaps by an alien civilization that has mastered interstellar travel but hasn't quite got the hang of parking. Slightly more realistic – though still unlikely – is that they were crushed by Nazi tanks during the war as saplings, before growing once again towards the light. Given that they are surrounded by the usual vertical trees we're accustomed to, this seems unlikely.

A natural explanation is that the trees ended up in a horizontal position as saplings, perhaps due to a storm or heavy snow, and this is how they developed their unusual shape. 

“It looks, to me, like a classic gravity response,” Gary Coleman, an associate professor of plant science and landscape architecture at the University of Maryland, told the Washington Post. “Whenever the stem is horizontal to gravity, the plant has a mechanism through which it can reorient itself.”

Coleman has seen such trees after storms while working in the US Forest Service. However there is another explanation, more likely than natural explanations. 

Traces of cuts and knots have reportedly been found on the trees, suggesting that humans may have kept them close to the ground during the early years of their growth, before allowing the gravity response to work its magic. It could be a tree farm, where the pines had been bent for use on curved furniture, frames or barrels, as naturally bent wood is stronger than straight wood that has been bent after being felled. 

We may never know what the true explanation is, though the human-made bends seems likely. Meanwhile, there is a much bigger tree-bending mystery: No matter where they are on Earth, Cook pine trees lean toward the equator.