Posted by Tony Bielaczyc
We're often reminding people, and ourselves, that gardening is an ongoing experience that requires patience, effort, experience, knowledge and a good dose of self forgiveness when something dies. It's not easy to come up with a plan, implement it and then watch your dreams fade because the wrong plant was put in the wrong place. Finding plants that are hardy enough to survive in your climate is one way around the phenomena of disappearing gardens. For generations, farmers, nursery growers and home gardeners have used a plant hardiness zone map as a guide to what will survive in their area.
The Zone Map was an effort to plot out and delineate regions of the continental U.S. based on the lowest average temperatures that can be expected in those regions (also called the 'average annual minimum temperatures'). Perennial plants that can make it through the winter intact and grow well the following season are said to be 'hardy' to that region or zone. Originally drawn in 1927 with information compiled at Harvard's Arnold Arboretum, the USDA decided to create it's own version in 1960. The results from the USDA put their map at odds with the original map put out by the folks at the Arnold.
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The Arnold map was considered the standard. In 1990, the USDA sought to create 'the' authoritative map with the help of of the National Arboretum. With the shifts in global climate, thoughts turned to revising the map and refining the previously acknowledged zones, still again. In 2001, the USDA funded research to compile and issue an updated version. The new map draft was released in 2003 and almost immediately created controversy. It was yanked from public use with claims of unsubstantiated data at its core. All this back and forth led to lots of conjecture and confusion for those same people it was meant to serve. Still another map is said to be in the works.
In the meantime, if you want the total in-depth history of all this drama, Tony Avent (the man behind the renown Plant Delights nursery) has it spelled out for you. In addition to the backstory, Tony also has some words of advice on how to use the map and how to interpret all those colorful bands that spread across the page. As with anything garden, there is a yin for somebody else's yang. When a plant label claims something can't survive in my South Brooklyn community garden, I've often got living proof that, indeed, it can.
'Microclimate' isn't just a fancy word that specialists bandy about. It's a realty that plays out everyday in almost every garden. Such is the reason for zone declinations like Z7a and Z7b. And within that, there is a whole lot of room for temperature nuance. Zone maps, no matter the origin, give us an 'average', not an absolute. The same goes for plant tags. In gardening, it really is all about patience, effort, experience, knowledge and a good dose of self forgiveness when something dies, right along side a hardy 'job well done' for all those successes.
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