Where are many foods imported from during our winter? Why can they grow food when we can't?

It’s obvious to anyone who visits an American supermarket in winter — past displays brimming with Chilean grapes, Mexican berries and Vietnamese dragon fruit — that foreign farms supply much of our produce.

Imports have increased steadily for decades, but the extent of the change may be surprising: More than half of the fresh fruit and almost a third of the fresh vegetables Americans buy now come from other countries.

Although local, seasonal and farm-to-table are watchwords for many consumers, globalization has triumphed in the produce aisle. And despite the protectionist “America First” message coming from the Trump administration, the growth in imports appears likely to continue.

So this is an apt moment to examine how the shift happened, and what it portends — good or ill — for American consumers and farmers.

“I had no idea that more than half our fruit is imported, and it shocks me that this has happened so quickly,” said Michael Pollan, a professor of journalism at the University of California, Berkeley, whose best-selling books have analyzed the tensions between local and global food systems

Explanation:

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)