Plants deal with the cold in a variety of ways, but how exactly they acquired those tools has remained a mystery. Now, after mapping out the largest time-scaled evolutionary tree to date, a group of scientists have key insights into how flowering plants evolved to withstand the cold.

According to the study, which involved a time-scaled evolutionary tree of more than 32,000 flowering plants, plant characteristics that help them survive in freezing temperatures probably first surfaced as a backlash to droughts or other environmental factors in lush areas.  

"This suggests that some other environmental pressure — possibly drought — caused these plants to evolve this way, and it happened to work really well for freezing tolerance too," said Amy Zanne from George Washington University.

Fossil records show that most early plants happened to live in temperate climates that were warm and conducive to leafy life. Despite their immobility once rooted, plants then spread to higher and higher altitudes, using various techniques to make it through the cold.

"Think about the air bubbles you see suspended in the ice cubes," said Zanne. "If enough of these air bubbles come together as water thaws they can block the flow of water from the roots to the leaves and kill the plant."

Researchers were also able to identify three key ways plants survive low temperatures. One group, consisting of plants like oak trees, lose their leaves during the winter months. Others evolved narrower water transport arteries so that the plant isn't as susceptible to freezing. Finally, a third group goes even further by dying all the way back to its roots.

You can read the full published study detailing the findings in the journal Nature.