What's Your Zone?

 

The SGI Plant Heat Zones Map

No, that's not the latest pick-up line. 

Do You Know What Your Heat Zone Is? 

If you've been gardening for any length of time, you probably know what hardiness zone you live in. But do you know what your heat zone is? While hardiness zones track the cold, heat zones track the summer highs.

  • Hardiness Zone = average annual extreme minimum winter temperature at your location, measured over a 30-year period.

  • Heat Zone = average number of days above 86°F at your location, measured over a 30-year period.

Both zones are important for maintaining healthy outdoor plants and climate-resilient landscaping.

Why Heat Zones Matter For Sustainable Gardening

Hardiness zones are only half of a plant’s survival story. If you’ve ever wondered why a plant that’s supposed to grow well in your hardiness zone struggles to survive or even dies during the summer, it's likely due to summer heat stress -- trying to grow it in the wrong heat zone.

At 86°F/30°C, a plant’s cell walls start to leak fluid, photosynthesis comes to a halt for most species, and the plants begin to shut down. Increases in temperature above this threshold for prolonged periods, especially during droughts, are likely to kill the plant altogether.

Like the hardiness zones, the plant heat zones have been migrating northward over several decades because of changes in the climate. As a result, plants that grew just fine for previous homeowners in your area may no longer thrive there.

This means that the original heat zone map, which was based on temperature data from 1974 to 1995, is no longer as useful as it once was.

Infographic comparing 1990s technology to modern interactive tools, highlighting the update from old AHS climate data to the new SGI Plant Heat Zones Map.

 Infographic comparing 1990s technology to modern interactive tools, highlighting the update from old climate data to the new SGI Plant Heat Zones Map.

This  infographic provides some perspective on how other tech that was popular in the early days of the older heat zone map have changed since then.

The Plant Heat Zone Map Gets An SGI Makeover 

At SGI, we always thought the plant heat zone map was a great idea. It just needed a complete overhaul, using more recent climate statistics, to bring it into the 21st century. 

Revolutionary changes in data collection and mapping software enabled us to build a brand new interactive plant heat zone map optimized for desktop, laptop, or phone.

New! 13 Zones Instead of 12

We mirrored the 12 intervals of the original heat zone map to maintain consistency, then added a 13th  Zone (>than 258 days vs. >210 days over 86°) to correspond with the USDA's 2023 Hardiness Zone map. This 13th zone captures the realities of extreme, increasing heat waves across the South and Southwest.

Find Your Own Heat Zone

Ready to adapt your garden for the future? check it out at Sustainable Gardening Institute Plant Heat Zones Map. 

Connect with SGI

We want to help communities adapt to these shifting climate realities:

  • Book a Presentation: To schedule a virtual presentation on SGI's new Plant Heat Zones Map for your garden club, environmental group, or other organization, email us at L.devries(at)sustainablegardeninginstitute.org

  • Join the Community: Follow our updates on Facebook and LinkedIn, and please share our interactive map with family, friends, and neighbors who care about the Earth.

Get Sustainable Gardening Tips Sent Straight to Your Inbox:

Sign up for the SGI Newsletter here to get seasonal advice, native plant recommendations, and climate-resilient gardening strategies delivered quarterly.






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