Every autumn, millions of little orange suns appear among the dark green leaves of small trees along the Black Sea coast of the Caucasus. These are ripening citrus fruits. But Adjara and Abkhazia still can’t supply enough mandarins and oranges to meet demand across the whole country. In places like Moscow or Murmansk, you can’t plant a mandarin tree — it would die at the first frost.
Scientists have long asked why trees freeze — and they may have an answer.
A birch branch was placed in a special chamber and cooled to -100°C. When it was brought back into the laboratory and set in a jar of water, it sprouted green leaves. A blackcurrant branch survived an even colder test — down to -253°C.
That suggests trees can fight frost on their own; they just need a little help to boost their cold tolerance. That would mean making plant cell walls more permeable to water. Biologists believe modern chemistry could make that possible.
If so, citrus and peach orchards could one day thrive along the shores of the Arctic Ocean.
