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Home » Local Food & Farm Buzz

New Planting Zone Map

By Helen Brody (February 23, 2012)

Most media reports about USDA’s recent unveiling of the updated Plant Hardiness Zone Map (PHZM) focused on the influence of warming temperatures and climate change. This is the familiar map found on seed packets and in nursery catalogs. For farmers, gardeners and scientists there’s a lot more to the precision and utility of the new online map tool.  For the first time, the plant hardiness zone map is geographic information system-based, and designed for internet use in a format that is searchable by zip code. Close-up maps are available for each state. The New Hampshire map, for example, shows new detail of zone differences within regions—such as areas of the warmer 6-a hardiness zone identified not just for our state’s Seacoast region, but also in an archipelago of green-shaded islands extending from parts of Cheshire County northward through parts of eastern Sullivan County.

The new map is the first major revision to hardiness zones since 1990. Numerous boundary adjustments were made in this map which is drawn to a much finer scale. Each zone represents the mean extreme minimum temperature for an area, calculated from the lowest daily minimum temperature recorded for each of the years 1976–2005. USDA cautions that this does not represent the coldest it has ever been or ever will be in an area, but is simply the average of lowest winter temperatures for a given location over this time period.

Some changes in the new map result from more sophisticated methods of mapping zones between weather stations. Algorithms now account for differences in elevation, proximity to large water bodies or urban areas, and position on terrain. Data was also used from many more weather stations than for earlier map editions.

The previous 1990 edition of the USDA map was drawn from 1974–1986 weather data. The longer 30-year period was chosen for the new map by the group of horticulture, botany, and climatology experts who led the latest revision. The longer period helps balance between smoothing out year-to-year weather fluctuations, and the concept that during their lifetimes, perennial plants mostly experience what is termed “weather” rather than “climate.” On its website, USDA notes that “Climate changes are usually based on trends in overall average temperatures recorded over 50-100 years. Because the USDA PHZM represents 30-year averages of what are essentially extreme weather events (the coldest temperature of the year), changes in zones are not reliable evidence of whether there has been global warming.” Find the map and more information at

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            This is tax reporting and preparation season, a time to review numerous aspects of farm and other businesses. Registration of the farm business name is one consideration that has traditionally been overlooked by many farm owners. Just as Apple has run into trouble with ownership of the iPad name in China, after buying up rights to the name in markets all around the world, farm-owning families can find themselves challenged to pay someone else for the ‘right’ to use a farm name used by a farm family for generations. Former Commissioner Steve Taylor advises this also becomes a factor when farmers begin to make and market value-added products.  The New Hampshire Secretary of State’s office has information on registering a business name or corporation (including LLCs), and a free site for searching the existing list of registered names at Click on ‘Starting a business in NH,’ and then click ‘Registering Your Business.’ A simple trade name must be renewed every five years, while corporate or LLC names require annual reporting and fee.  Contact the Secretary of State Corporate Division Monday through Friday 8:30am – 3:30pm at State House Annex Room 341, 25 Capitol Street, Concord, NH 03301 or 603-271-3246.

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