ARIZONA NEWS

Arizona mostly holds ground, but plant hardiness zones get major national adjustments

Nov 18, 2023, 6:20 PM | Updated: Nov 20, 2023, 12:30 pm

U.S. plant hardiness zones...

Southwest U.S. plant hardiness zones. (USDA)

(USDA)

PHOENIX — The U.S. Department of Agriculture’s “plant hardiness zone map” was updated Wednesday for the first time in a decade, depicting the impact climate change will have on gardens and yards across the country.

Although changes are substantial in some regions of the country — Southern staples like magnolia trees and camellias may now be able to grow without frost damage in once-frigid Boston, for example – in Arizona and the Southwest, changes are limited.

Minor changes in Arizona

Most of the Phoenix area remains in 9b and 10a zones. Zone 9b is an area with average annual extreme minimum temperatures of 25 to 30 degrees.

Zone 10a is an area with average annual extreme minimum temperatures of 30 to 35 degrees.

Boston University plant ecologist Richard Primack, who was not involved in the map project, said: “Half the U.S. has shifted to a slightly warmer climatic zone than it was 10 years ago.” He called that “a very striking finding.”

As the climate shifts, it can be tricky for plants — and growers — to keep up.

“There are a lot of downsides to the warmer winter temperatures, too,” said Theresa Crimmins, who studies climate change and growing seasons at the University of Arizona and was not involved in creating the map. “When we don’t have as cold winter temperatures, we don’t have as severe die-backs of insects that carry diseases, like ticks and mosquitoes.”

She added that hotter, drier summers in some regions may kill plants that once thrived there.

“You wouldn’t want to plant plants that aren’t adapted right now for where you’re living,” she said.

Uneven climate

Climate shifts aren’t even — the Midwest warmed more than the Southeast, for example. But the map will give new guidance to growers about which flowers, vegetables and shrubs are most likely to thrive in a particular region.

One key figure on the map is the lowest likely winter temperature in a given region, which is important for determining which plants may survive the season. It’s calculated by averaging the lowest winter temperatures of the past 30 years.

Across the lower 48 states, the lowest likely winter temperature overall is 2.5 degrees warmer than when the last map was published in 2012, according to Chris Daly, a researcher at Oregon State University’s PRISM Climate Group, which collaborates with the USDA’s Agricultural Research Service to produce the map.

Primack said he has noticed changes in his own garden: The fig trees are now surviving without extensive steps to protect them from winter cold. He has also spotted camellias in a Boston botanical garden and southern magnolia trees surviving the past few winters without frost damage. These species are all generally associated with warmer, more southern climates.

Winter temperatures and nighttime temperatures are rising faster than daytime and summer temperatures, Primack said, which is why the lowest winter temperature is changing faster than the U.S. temperature overall.

The Associated Press contributed to this report.

We want to hear from you.

Have a story idea or tip? Pass it along to the KTAR News team here.

Arizona News

The auction will feature more than 1,300 professionally appraised lots. (Sierra Auction Photos)...

David Veenstra

Arizona Department of Revenue to auction off unclaimed property

The Arizona Department of Revenue is auctioning off unclaimed property from abandoned safe deposit boxes this week.

3 hours ago

Shopping center developer Macerich withdrew its proposal with the city of Phoenix's planning hearin...

KTAR.com

Macerich pumps brakes on proposal for new Biltmore office tower

Prominent shopping center owner and developer Macerich Co. is delaying its plans for a new Class A office building.

4 hours ago

Persian New Year Festival...

KTAR.com

Annual Persian New Year Festival adds fashion show, musical performance to schedule

This year's version of the Persian New Year Festival will feature three events over four days starting Feb. 28 in Scottsdale.

14 hours ago

42-year-old Joseph D. Eschief (left), 27-year-old Antonio N. Eschief and 46-year-old Selena Dewey. ...

KTAR.com

4 people stabbed during early-morning melee at Scottsdale bar

A suspect is in custody after four people were stabbed early Saturday during a violent altercation at a bar in Scottsdale.

14 hours ago

Phoenix Fire...

KTAR.com

Occupant dead after vehicular crash leads to flames in Phoenix

One person died and two others suffered non-life-threatening injuries after a vehicle crash sparked a fire in Phoenix, authorities said. 

15 hours ago

Republican presidential candidate former President Donald Trump hugs and kisses the American flag a...

Associated Press

Trump calls himself a ‘proud political dissident’ in CPAC speech

In a CPAC speech, Trump painted an apocalyptic vision of the future if President Joe Biden wins again as the two prepare for a rematch.

16 hours ago

Sponsored Articles

...

Collins Comfort Masters

Here’s 1 way to ensure your family is drinking safe water

Water is maybe one of the most important resources in our lives, and especially if you have kids, you want them to have access to safe water.

...

Day & Night Air Conditioning, Heating and Plumbing

Valley residents should be mindful of plumbing ahead of holidays

With Halloween in the rear-view and more holidays coming up, Day & Night recommends that Valley residents prepare accordingly.

...

Sanderson Ford

The best ways to honor our heroes on Veterans Day and give back to the community

Veterans Day is fast approaching and there's no better way to support our veterans than to donate to the Military Assistance Mission.

Arizona mostly holds ground, but plant hardiness zones get major national adjustments