New USDA Plant Hardiness Map

After years of discussion and debate, the new USDA Plant Hardiness Map is ready. The previous map was developed in 1990. The new gardening zone map, broken into zones of ten and five degree termperature increments, now has thirteen zones with the newest zones 12 and 13 having low winter temperatures  of (50-60 degrees F) and (60 - 70 degrees F). For background on how the new map zones were arrived at, Tony Avent with Plant Delights Nursery in Raleigh, NC, one of my favorite plant catalog nurseries in the world, was a part of it from the beginning and provides history:

On August 18, 2004, USDA formed a technical review committee of 23 people including yours truly. The group consisted of nurserymen, crop researchers, foresters, climatologists, and others. The committee had a number of meetings at the USDA headquarters in Maryland and many subsequent meetings by phone.

The details of the map making process was quite fascinating. The first few meetings were spent hashing out what we wanted in the map. Several of us had pushed for a 30-year map, which would more closely echo short term natural temperature fluctuations, and the USDA agreed. Another of my requests to create an a, b, c, and d breakdown for each numbered zone was delayed until the future.

We also wanted a map that would allow more temperature interpolations between weather stations, which would take into account things like lake and mountain effects which were missing in the previous map. The process then progressed to the USDA to gather the data and create the map with their in-house staff. A complication arose when their in-house algorithm specialist was commandeered by the Department of Defense and sent to Afghanistan to run algorithms to locate Osama bin Laden. During this time, the specialist would join us via conference call from a safe place in Afghanistan...I’m not making this up.

After two years, the map was supposedly ready as the committee members gathered in Maryland for the unveiling. We were never privy to exactly what went wrong, but the map we saw showed all of the US getting colder, which was certainly not the case. My best guess is that someone reversed all the data. After this debacle, the map trail went cold for nearly a year, during which time the USDA decided in 2007 not to complete the map in-house, but instead to outsource the project to the PRISM (Parameter-elevation Regressions on Independent Slopes Model) Climate Group at Oregon State.

After PRISM completed their initial map, we were shown a draft map via phone conference. The rest of the year was spent going back and forth about areas which the review team felt were not zoned correctly. During this time, more data sites were added to those regions of concern, either from Canadian, Mexican, or military data. Finally in April 2008, the technical review team finished their work and the map was back in the lap of the USDA for publication. The subsequent 3 years and 9 months were spent by USDA trying to figure out what colors to make the zones and then finding a website that could host the map without crashing like their previously launched food pyramid...I’m not making this up. Whoever said that the Federal Government moves slowly was spot on...hence the reason the most recent climatic data in the map is 6 years old.

The USDA map has two versions, a static map where you can select your state and zone or the interactive map where you can input your zip code and you go right to your city and find your gardening zone.

The new map reflects the warmer temperatures from microclimates from winds, bodies of water, slope of the land, and urban heat islands but the USDA makes a valid point that this new realignment should not be used as an indication for global warming.

I agree. The previous USDA map from 1990 used data from a twelve year time period of 1974 to 1986.  The new map uses data from the years 1976 to 2005. The weather is cyclical and since 2005 I've seen even colder temperatures during the winter here locally than normal.  It will be interesting to see the next gardening zone map to see if the two-thirds degree higher temps reach one degree.

Find out more about Plant Delights Nursery:  A Delightful Day Filled With Plants

Free Guide To Identifying Southern Invasive Plants

The USDA Forest Service Southern Research Station has created a free pdf download of invasive plant species, “A Field Guide for the Identification of Invasive Plants in Southern Forests.”

The book is a more comprehensive identification guide to nonnative trees, shrubs, vines, grasses, ferns and forbs invading the region’s forests and other natural areas. The revised guide includes 23 more plant species with updated information on the original 33 species; 241 new photos and images and a new “Resembles” section so users can identify plant “look-alikes.”

The book’s appendix contains the most complete list of nonnative invasive plants in the 13 Southern states, providing common and scientific names for 310 other invading species including, for the first time, aquatic plant invaders.

Complete with color high density photographs, it takes a few minutes to download or you can email:

To: pubrequest@fs.fed.us
Subject: Publication Request
In email, type: Please send me: A field guide for the identification of invasive plants in southern forests (GTR-SRS-119) by Miller, James H.; Chambliss, Erwin B.; Loewenstein, Nancy J.

This publication should be in every Master Gardener Clinic, County Extension office, Master Naturalist, eco-tourism guide, and environmentalist's library. The pdf is an updated version of their original publication from 2003.

In Your Backyard: "Gray Skies Are Going To Clear Up"

Last week's "In Your Backyard" radio show was a "Best Of" so that I could stay in bed and recover from a very bad cold. I still have a cough and a frog in my throat so listening this morning, you'll probably hear it.

Last weekend was the 2010 UF/Natural Resources Leadership Institute (NRLI) graduation for Class IX. The graduating fellows are an exciting and diverse group of environmentalists, municipality, federal, and state agency representatives. The class's final tour event and NRLI board meeting was held at Rosie Koenig's Organic Farm in Gainesville. There is so much to learn about the intricacies of growing and marketing organic vegetables.






On today's show - organic gardening - what does it mean?

USDA - Organic Gardening

On Sunday, we went to Leu Garden's Plant Sale in Orlando. What a great event! Great plants, unusual gardening items! I was able to bring home nun's orchids, vanilla orchid, smoke bush, and herbs.


Will update with your phone calls this afternoon!