LEILA FADEL, HOST:
People in Fairbanks, Alaska, are waiting for the dramatic arrival of spring. It's called greenup, when birch and aspen trees put their leaves out in a rapid burst and many of the hills turn green seemingly overnight. It's forecast to happen in the next few days. NPR's Ravenna Koenig reports.
RAVENNA KOENIG, BYLINE: When botanist Jan Dawe moved up to Fairbanks in 1975, the first greenup she saw felt like magic.
JAN DAWE: To be able to watch the same tree at 8 o'clock in the morning, noon, 6 o'clock at night, and you could see that they were growing.
KOENIG: Dawe works for the University of Alaska Fairbanks and is part of a group that tracks greenup each year. Birch and Aspen make up a big part of the region's greenery. And while some shadier areas can take longer, often, a lot of the trees go from bare to leafy in a shocking 24 to 48 hours.
DAWE: The forest turns from the dull gray of winter into this fresh green burst.
KOENIG: What explains this rapid leaf-out? To start, Dawe says, Fairbanks is right at the northern edge of where trees grow, less than 200 miles below the Arctic Circle. It's super cold and dark in the winter, and not many types of trees grow in this region.
DAWE: You have to really be a survivor.
KOENIG: Further south, Dawe says, trees may have seven months to soak up the sun through their leaves and make it into food. But in Fairbanks, it's more like four.
DAWE: And if you're going to be a successful plant, you have to get your leaves out there.
KOENIG: In other words, these trees have evolved to take advantage of the growing season the second it arrives. When is that? Depends year to year. Being so far north, Fairbanks is now getting a whopping 18-plus hours of daylight, which can supercharge plant growth. But the ground also has to thaw enough - and that's the unpredictable part - that the roots can pull up water and make it into sap, which then goes to every single branch.
DAWE: Every single winter bud. It feeds it in order for it to have the energy it needs to grow and then open up.
KOENIG: For those who live in this area, it's a big moment. Winter is long for people as well as trees.
HANNAH HILL: Snow's on the ground. My yard is flooded. My dog is soaking wet, and I'm like, it's coming. It's going to be spring. It's going to be summer.
KOENIG: Hannah Hill lives in Fairbanks and calls greenup a seasonal holiday.
HILL: I'd like to celebrate it by hooting and hollering and carrying on and texting everybody I know that I love them and that we did it. And here you go.
KOENIG: Hill also runs an annual pool where people bet on the day greenup arrives. This year, over a hundred people participated and are watching their windows for that pop of green.
Ravenna Koenig, NPR News.
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