USDA Map and Green Roofs

By Jörg Breuning, The Green Roof Patroller

Not many people may know:

In 2002 the USDA (United States Department of Agriculture) initiated a project with the American Horticultural Society (AHS) to update the 1990 USDA Plant Hardiness Zone Map.

A year later the AHS released a draft of the update version which showed that many of the hardiness zones had moved northward reflecting a general warming trend.

The USDA, after a brief review, decided to reject the draft and gave little justification for its decision.  Its terse dismissal raised the possibility that it was a political decision - the USDA was concerned that the AHS Draft gave support to global warming proponents and decided to suppress the project to avoid controversy and not embarrass the Bush Administration.

2012 Hardiness Zone Map - graphic by Jörg Breuning.

Ten years later the USDA released the 2012 Hardiness Zone Map which added two new climate zones and showed a general warming trend across the country.  The USDA, however, noted that, "Changes in zones are not reliable evidence of whether there has been global warming."

In our experience, the USDA Plant Hardiness Zone Map is not very useful for green roof installations to start with and in general the increasing speed of climate shift may require an update every five years.

With more updated maps the USDA could also include precipitation and precipitation trends since vegetation is less depended on temperature than on naturally occurring water – if we don’t want to waste valuable water resources and capital through artificial irrigation.

Experienced Green Roof experts and professionals are monitoring and analyzing the locally occurring vegetation.  Based on that they are able to make assumption what species can have the highest chance for survival and able to sustain as long as the building lasts.

In contrast, a one-size-fits-all green roof system or pre-grown system might not be a good choice for certain clients – even when the USDA Map or the roofing manufacturer tells a different story and when USDA research is utilized as a political instrument.

The good news: Plants don’t care about politics!

Jörg Breuning

Jörg Breuning, principal of Green Roof Service LLC/Green Roof Technology

In his own words, Jörg was born in the green roof capital of world. He began working with green roofs in Stuttgart, Germany in 1980. Since then, he has installed and maintained tens of millions of square feet of green roofs throughout the world.  Remember, everyone, that English is not his mother tongue!

During his career Jörg has earned multiple degrees and certifications in landscaping, horticultural, and green roofing. In January 1983, Jörg Breuning was one of the first people in the world to earn a green roof professional accreditation from Optima, now Optigrün AG, who were the first green roof manufacturer to offer an in depth educational system for the installation and maintenance of their products. In order to be eligible for the accreditation, a candidate had to have completed 3 years of apprenticeship with a certified landscaping company. In 1985 he earned his national certification and horticultural technician degree – a program of work and study that required 5 years of practice in an approved landscaping company and 4 semesters of University study.

In 2003 Jörg transferred his German Company (founded in 1985) to the United States after being the key consultant for Chicago’s City Hall green roof. As an experienced horticultural expert, he has been able to educate many of North America’s green roof pioneers, providing them with fundamental green roof knowledge to start and grow their own businesses.

His company Green Roof Service LLC (Green Roof Technology) has introduced numerous innovations to the North American green roof industry. Many of these innovations have been adopted by companies such as Roofmeadow, Emory Knoll Farm, GAF, CETCO, Rooflite, Green Roof Solutions, Celebrity Cruises Miami and Optigreen.

Jörg’s articles will strongly focus on topics that ensure common sense is always practiced, ensuring that the horse stays in front of the cart, and provide valuable insights into making green roofs as popular and efficient as they are in Europe.

Contact Jörg at jorg (at)

Past Green Roof Patroller Articles

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