Hardiness Zones

February 20, 2016

I moved from Kansas to Arkansas a couple of years ago and have a few questions, such as: what is our planting zone?

It depends on which USDA Hardiness zone map you are using to determine what zone Arkansas is in.  In the older version which is still used by many gardening books and catalogs, NW Arkansas was zone 6 (average winter low temperature -10 to 0), the central part of the state was zone 7 (0-10) and the southern tip was zone 8 (10-20 degrees for the average low temperature).  After years of milder temperatures, in 2012 the USDA came out with a new zone map.  The southern third of the state is now zone 8a (10-15 degree low) with the next tier moving north zone 7b (5-10 degree) and the next third 7a (0-5 degrees). Keep in mind, the only piece of information you get from a zone map is the average low winter temperature—not summer temps, rainfall, humidity, etc.  So don’t use this as your Bible when choosing plants, it just gives you some guidelines.

(March 2012)

USDA Hardiness Zone Map changes for 2012

The USDA Hardiness zone map has been around for many years, and is a planting guide giving the average low winter temperature in regions across the United States.  Recently it was updated to reflect the more moderate winter temperatures.  Arkansas still has three different hardiness zones (6-8), but they have shifted.  Zone 8a, with an average winter low temperature of 10-15 degrees now encompasses almost half of the southern part of our state, leaving only a fringe of zone 6b  in a few northern locations with an average winter low of -5 – 0 degrees F.  The remainder of the state is in zones  7a and 7b with a range of 0-10 degrees F.  This zone map should be used as another reference tool when choosing plants, but do keep in mind that it only gives you one piece of the puzzle—average low temperature.   It does not compare summer high temperatures, rainfall, humidity, or other weather patterns.  It would be helpful when looking at a catalog of plants, for example, if it tells you the plant is hardy from zone 2-7, you would know that the plant was very cold tolerant—zone 2 can get as cold as 50 degrees below zero.  Zone 7 would be the warmest it could tolerate, so it might struggle in the heat and humidity of the south.  On the flip side, if it was hardy from zone 7 – zone 10, you would be the coldest zone it could survive in.  But try new plants.  You aren’t a gardener, if you have never lost a plant—experimentation may give you some new favorites.

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