With California’s New Hardiness Zones Comes Change

California gardeners are adjusting to the effects of climate change, thanks in part to recent updates to the USDA Hardiness Zone Map. As spring gardening season beckons planters outside, a number of zip codes in the state have seen half-degree shifts, mostly to the next warmer half zone. Although the USDA states approximately 50 percent of country has migrated to warmer zones, the department also asserts temperature change to plant hardiness zones isn’t necessarily an effect of global climate change.

Scientists at California Climate Hub disagree, as temperatures have been rising for nearly 120 years. The same can be expected of the future, when “climate change means warmer average winter temperatures and warmer extreme cold temperatures.” Likewise, horticulturists at Evergreen Nursery, a local, independent nursery and garden center in San Leandro, have seen increased interest for California natives and drought-tolerant plants. Rising temperatures and plant hardiness zones not only affects the environment, but also the producer, buyer, and seller.

“Clients are buying a lot of drought-tolerant plants,” states Larry Mendez, an Evergreen Nursery employee. “We teach them how to not use as much water. We give them options for a changing world.”

Adapting to a changing world is necessary for all of us. What do changes in hardiness zones then mean for Californians?

National production is affected

California’s Central Valley is one of the most robust crop-producing regions in the world. Even though farmland accounts for only 1 percent of U.S. farmland, local farmers supply approximately 25 percent of the country’s fruit, nuts, and other food products. The shift in USDA hardiness zones particularly affects the Central Valley, which scientists project will “change from zone 9a to zone 9b by the 2050s, and to zone 10a by the 2080s.” This, in turn, affects food production across the country.

Californians can expect more – and less – rain

While it’s easy to assume increasing temperatures (and, subsequently, in hardiness zones) means a decrease in rain, meteorologists predict more wet and more dry extremes in the future. The Institute of the Environment & Sustainability at UCLA states, “Under a scenario of rapidly increasing greenhouse gas concentrations, extremely dry and extremely wet events become more common over the course of this century.” The answer is both for California gardeners.  

Native plant gardens will increase

When data from a recent study allowed scientists to create a “statistical model that predicts what temperatures and rainfall amounts each species preferred” (and didn’t merely tolerate), scientists were able to identify mismatched plants to their respective, often adapted environments. Plants, in other words, told scientists where they wanted to live.

As awareness around plant preference increases, native plant gardens will certainly increase across the state.