Jeff Masters Weather Blog

What you need to know before you buy garden perennials this spring » Yale Climate Connections


As spring approaches, many gardeners are looking for new perennials to add to their collections. As the climate warms, some may want to try growing plants that historically only survived farther south.

The USDA recently updated its Plant Hardiness Zone Map for the first time in over a decade.

The map assigns every location in the U.S. to one of 13 zones, each with an A and B half-zone. Knowing the zone they’re in helps gardeners determine which plants will survive winter in their region.

Daly: “So you can think of the plant hardiness zone map as a plant selection guide. It’s focused on just one measure, which is the extreme lowest minimum temperature of the year, and that’s averaged over 30 years.”

Chris Daly of Oregon State University leads the Prism Climate Group, which helps create the map. He says in the updated version, about half the country shifted a half-zone warmer.

The biggest changes occurred in states such as Kansas, Missouri, Tennessee, and Kentucky.

Daly cautions that the changes are subtle and extreme cold snaps remain possible.

Daly: “I think what I would start doing is look around your garden and look at the microclimates that occur within your garden. … You may be able to grow some new plants in some of these warmer microclimates.”

Reporting credit: Sarah Kennedy / ChavoBart Digital Media





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