Introducing The Updated USDA Hardiness Zone Map

Introducing The Updated USDA Hardiness Zone Map

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Choosing which plants to grow begins with knowing your growing zone! Also called the Planting Zone or Hardiness Zone. This allows you to choose the right plant for your area. Knowing your Zone and the Zone Range of your plant ensures it will survive the hottest summers and coldest winters that are typical in your area.

Introducing the USDA’s first updated Plant Hardiness Zone Map since 2012!

The Hardiness Zone Map

Ranging from zone 1, being the coldest, to zone 13 being the warmest, each zone is divided into half zones designated as ‘a’ and ‘b’. Plants are listed as being suited for a range of zones, and gardeners in Zone 6a can grow plants rated for Zone 6 in general. So if a plant's range is 3 - 7, a Zone 6 gardener should have success.

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Remember that microclimates and elevation can also play a significant role in changing your zone ever so slightly.

To find your current zone, or see if your area has changed, enter your ZIP code on the Hardiness Zone map on the Nature Hills website, or at this link: https://planthardiness.ars.usda.gov/

The USDA website also has average temperature highs and lows and the ranges each growing zone typically experiences listed for you.

What A New Hardiness Zone Map Means For You

As of late, the US has experienced some milder winters across the nation, which means that some plants may be able to be grown a bit further north than they used to. Some areas are becoming more arid while others are experiencing increased rain/snow, plus stronger storm systems and temperature fluctuations.

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The updated USDA Plant Hardiness Zone map is based on 30 years (1991 to 2020) of annual high and low averages throughout the year.

The new Hardiness Zone data, along with the addition of more temperature stations and better mapping techniques, shifted about half the country into a warmer half-zone. For example, those in zone 6a may shift into 6b, and those in zone 6b may shift into 7a.

A zone 6a at high altitudes may need to look for plants hardy in zone 5 instead. However, gardeners in zone 5b now may now get away with planting some zone 6 plants as trends begin to shift slightly warmer!

Native plants naturally react to these gradual changes on their own; migrating to areas that are better suited for them because of the shift in temperatures. Bringing with them their host of pollinators and wildlife that rely on them.

Other Hardiness Zone Change Reminders

Gardeners should recognize that many other environmental factors, in addition to hardiness zones, contribute to the success or failure of plants.

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Plants need the proper amount of light. With the new Hardiness Zone changes, plants that require partial shade, and are grown at the limits of your Hardiness Zone may be injured by too much sun during the winter because it might cause rapid changes in the plant’s internal temperature.

Soil moisture might vary seasonally, and new plants that might otherwise be hardy in your Zone may become too dry in late autumn in areas that have shifted slightly hotter or are becoming more arid in the winter. We do provide these important cultural tips on each of the plants that we sell.

Knowing this helps you prevent dormant plants from suffering moisture stress and heat stress.

  • It’s important to understand that previous weather records cannot provide a guaranteed forecast for future variations in weather.
  • Wind, soil type, soil moisture, humidity, pollution, snow, and winter sun can greatly affect the survival of plants.
  • Urban versus Suburban environments can also have subtle differences
  • Heat and moisture balance is important
  • Other factors include the way plants are situated in the landscape, how they are planted, and their size and health can also influence their survival.
  • Warmer or wetter conditions may allow new pests/invasive species that may not normally survive in your area, to suddenly gain a foothold.

Natural Weather and Climate Cycles

This gradual shift is simply part of the natural cycles of our planet. According to the USDA Climate Change Resource Center, major glacial (cold) and interglacial (warm) periods are caused by Milankovitch cycles (changes in Earth’s orbit around the Sun) and have occurred at varying intensities throughout periods ranging every 10,000 - 100,000 years.

Atmospheric CO2 concentrations may cause changes, as does warming or cooling caused by orbital changes every 1000 years. Solar radiation changes also affect the Earth’s surface temperatures. 

There are also shorter cold/warm cycles that occur on approximately 200 - 1,500-year cycles, such as the Medieval Warm Period (900 - 1300 AD) and the Little Ice Age (1450 - 1900 AD).

Interannual to Decadal climate cycles, including the most well-known El Niño-Southern Oscillation (ENSO), last 9 to 12 months and can cause rainier/snowier years and drier years. 

Other cycles can bring about drought, increased summer heat waves, flooding, and other unusual spikes of cold or heat leading to record highs and lows.

Time For An Update!

For many of us, the new USDA Hardiness Zone map won’t impact our day-to-day lives much. But for a select few, the changes just might bump you into a growing zone that will allow you to grow that plant of your dreams! Or might cause a favorite in your landscape to begin to struggle.

Reach out to your local County Extension Office for plenty of regional information and other local tips and tricks for your area! Plus, Nature Hills has #ProPlantTips for Care to help you install your new landscape additions perfectly!

Happy Planting!

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