Tip Of The Day - 8/21/05 - Hardiness Zones

Discussion in 'Industry Surveys & Polls' started by Sean Adams, Aug 21, 2005.

  1. Sean Adams

    Sean Adams LawnSite Gold Member
    Messages: 3,597

    Found this and thought it would be a good "tip"

    Probably the most important consideration in determining what garden and landscape plants you can grow is whether or not they will survive the climate in your area.

    The USDA Plant Hardiness Zone Map factors in average winter minimum temperatures. This collection of information starts with Zone 1, where minimum temperatures can go down to MINUS 50 degrees Fahrenheit, and ranges to Zone 11, for the lucky gardeners in Hawaii and extreme Southern Florida where lows don't drop below 40 degrees Fahrenheit.
    The data on which the USDA map is based was gathered over a period of 60 years.

    (First number on left is zone, number to right is temperature in farenheit)

    1 Below -50 F
    2a -50 to -45 F
    2b -45 to -40 F
    3a -40 to -35 F
    3b -35 to -30 F
    4a -30 to -25 F
    4b -25 to -20 F
    5a -20 to -15 F
    5b -15 to -10 F
    6a -10 to -5 F
    6b -5 to 0 F
    7a 0 to 5 F
    7b 5 to 10 F
    8a 10 to 15 F
    8b 15 to 20 F
    9a 20 to 25 F
    9b 25 to 30 F
    10a 30 to 35 F
    10b 35 to 40 F
    11 above 40 F
  2. Guthrie&Co

    Guthrie&Co LawnSite Senior Member
    from nc
    Messages: 784

    sometimes i will go a zone less to protect yourself from winterburn is it is questionable on the shrubbery selection
  3. ALSO very important to consider the heat index zones for your plants!
  4. Critical Care

    Critical Care LawnSite Bronze Member
    Messages: 1,654

    The Sunset Gardening Books are often considered to be the bibles for gardening and plant information. These books however use their own plant hardiness scale, but along with detailed zone maps - some very specific to certain areas - they mention the pros and cons for each zone, which plants do well, and which ones don't.

    Microclimates also play a big role in choosing the right plant for the right area. For example, there's a large difference between where I live and where people live just a few miles to the north... though the USDA zone will show us as being in the same zone. Consider your microclimate to be your "fine tuning".
  5. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    Critical Care is correct,Sunset's Western and Eastern Garden Books break down the states hardiness zones much more specifically than USDA zones do.
    Sunset developed the Heat Index Zones.
    The USDA zones were developed for farming not for ornamental gardening they are much too general and don't have a Heat Index Zone at all.
    Sunset Western Garden Book
    Sunset Eastern Garden Book
    Are THE best to go by because most ornamental nurserys and growers tag their plants using those zones and not USDA zones...at least here in the western states they do.
    The best Encyclopedia of Plants though in my opinion is
    The American Horticultural Society A-Z Encyclopedia of Garden Plants /Millinium Limited Edition.
    It has over 6000 pics and 15,000 Plant descriptions and cultivation descriptions for each.What kind of sun/shade and soil they need.If you make your living planting ornamentals(plants,tree's,shrubs ect)I strongly recommend you invest in this wonderfull book.It will blow your mind!It also uses the same zones Sunset does.
    Now some older books still use the USDA zones including old Sunset books so Keep your eye out if you use an old gardening book.
  6. Critical Care

    Critical Care LawnSite Bronze Member
    Messages: 1,654

    I was just glancing at my Sunset book and it has a chapter in it stating how the USDA climatic zones are based, which is upon winter minimum temperatures. Sunset uses this information, the information that Timturf mentioned (the American Horticultural Society heat zone system), elevation, humidity, rainfall, and other factors to come up with their rating. Over the years Sunset has gotten more detailed, especially in some areas, breaking down zones into subzones, etc. Hopefully they keep at it because I'd like to see some of the colder zones, such as mine, detailed a bit more.

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