You Might Think You Know What Zone You Are…

USDA Plant Hardiness Zone Maps help gardeners determine which plants are most likely to thrive in a location.  If you are like me, any time you hear about a new plant that you might want to add to your garden – your first question is probably what zone is it hardy to?  Even when gardening with native plants, you have to keep zones in mind. For example, NY state, where I live, covers zones 3-7.   So there might be plants native to NY in zones 6 or 7, but they aren’t for me - since where I am it is a zone 4 (or at least I thought it was! – more on that in a second).

You are probably very familiar with what zone you are gardening in – or at least you think you are!  In late January USDA released a new version of hardiness zone maps for 2012. You might think you know what zone you are – but it turns out you might be wrong according to the new maps!

the newly released 2012 map

Hardiness zones are based on the average low winter temperature. Zones are divided by 10 degree increments, with a and b subsections for 5 degree increments.  In the new 2012 maps many locations across the country shifted and became a subsection warmer.  So if you were a 5a you might now be a 5b, and if you were a 4b you might now be a 5a.  This new map is based on 30 years of temperature data, from 1976-2005, and was created with new and improved algorithms that took elevation and other terrain features into account. The old maps were based on a shorter and older temperature record, and simpler modeling, so they had become out-dated.  The new maps are much more accurate for our current conditions.

Another great thing about the new map is that it is also now interactive – so it is much easier to see exactly what zone you are in. You can just enter your zip code and ta-da – the site will tell you what your new zone is!   Click here to go to the USDA site and enter your zip code.

According to the older map, our nursery used to be a 4b. So I have always stuck with zone 4 plants to play it safe.  But now we are a 5a according to the new map.

 

 

Whenever you are buying plants for the garden, you of course want to make sure they will be hardy to your location.  This shift means that some of us might be trying out a few new plants in our garden and see how they do!  For example, Inkberry, Ilex glabra, is listed on many lists as hard to zone 5-9.  Although Cullina notes in his Native Trees and Shrubs book that if sited carefully, it can be hardy to zone 4.  I have been growing Inkberry at the nursery because it is such a great native alternative for many other non-native evergreen shrubs such as boxwoods used in landscaping around house foundations, but not in large amounts, because I was nervous about it overwintering.  Now of course, my site conditions haven’t changed from last year to this year, but now with the new maps, I have a bit more confidence in this plant for our area.

Inkberry, Ilex verticillata, is a great native alternative for foundation plantings.

Did your zone shift too? If so, what new plant might you try out this year that you hadn’t tried before?  I might add some Sweetspire, Itea virginica, a great native alternative to the popular non-native butterfly bush, to some of my plantings and see how it does.  According to the new maps – it should do just fine!  But I think I will do some testing on my own first for my site conditions. After all, algorithms and equations are great, but they aren’t Mother Nature!

© 2012, Emily DeBolt. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us

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    About Emily DeBolt

    Emily has a Bachelors degree from Cornell University and a Master's of Environmental Interpretation from the State University of New York College of Environmental Science and Forestry. She lives with her husband Chris and Greater Swiss Mountain Dog McKinley in northeastern New York where they run Fiddlehead Creek, a 100% New York native plant nursery that specializes in growing plants for water quality and conservation projects.

    Comments

    1. Donna@Gardens Eye View says:

      I was pleased to see we went up a half a zone here on the S shore of Oneida Lake. Still a zone 5 so I won’t be trying anything for zone 6 since it is never quite hardy here. I also am planting inkberry as an alternative and have Itea virginica.
      Donna@Gardens Eye View recently posted..Seasonal Celebrations-A Dream of Spring

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    2. Sue Sweeney says:

      If you’re sticking with local natives (and good for you if you are!), they are good, by definition, at your temperature range and you don’t need the Zone map.

      However, the changes in the Zone map do let you know that it’s is, most def, getting warmer. Eek!

      Reply
    3. Sue Sweeney says:

      Oh, I forget perennial herbs and fruits as something even the native purist need the Zone chart for.

      A downside of the warming temperatures: plants which were once fairly well-behaved in the garden are now becoming invasive. I’m now regularly chopping rose-of-Sharon and Bradford pear in CT.

      Reply
    4. Debbie Roberts says:

      Emily, My zone has remained unchanged, 6b, but I can definitey see the zone creep around me. I have to admit I’m a little surpsied by that since I do grow a few zone 7 plants which seem to overwinter, at least during most years, without any issues.
      Debbie Roberts recently posted..You Can Grow That ~ Connecticut

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    5. Leanne@landscaping brisbane says:

      I wonder if the zones are changing because of climate change or is it because we just have more accurate data and better modelling systems. It’s great to have a guide for growing plants but you often find many different microclimates within one zone anyway. That’s why it’s always best to chat to older gardeners or your local nursery to find out what’s best for your garden.

      Reply
    6. Kathy @nativegardener says:

      The new zones haven’t really affected me here in SoCal. I plant natives of the Santa Monica Mtns, and they are just as happy 5dgs this way or that :-) But good to have this resource as the country is changing.
      Kathy @nativegardener recently posted..Milkweed for the Love of Monarchs

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