Re: Re: Re: New USDA Zone Map
> Just curious, but Daryl do you feel the old one was 100percent accurate?
Heck NO! But it was closer. For example, I used to be listed in Zone 7a,
though I'm microclimatically in 6b because of my elevation. That's not too
bad, and is to be expected, given the broad nature of the zone maps. To put
me in zone 8 is ridiculous. We've had temps below zero most of the 20 years
I've been here. Even during these last few warm years, we've had low temps
in the 3-8 degree range.
The old zone map also showed a distinction between 7a and 7b. The dividing
line is roughly along the Chattahoochee River and Lake Lanier ( about 6
miles to the East of me). A quick drive during spring or fall was enough to
show the difference, as does a study of the plants that survive/thrive. The
difference is largely due to elevation, with the 7b areas somewhat lower.
(And yes, I'm painting with a broad brush, realizing that there are
microclimates, drainage differences, etc. which impact plant survival.)
Moving south and east of Atlanta, the elevation falls even farther (as well
as being farther south) with areas like Macon and Augusta being "below the
gnat line" and definitely in zone 8.
Atlanta itself has grown large enough to develop its own microclimate, with
radiated warmth from concrete and brick, so that several palms, Aspidistra,
and other less hardy plants will grow there. Zone 8 maybe but a prolonged
Alberta Clipper takes its toll every few years, not to mention the harsh
years of the early 80's, when Atlanta went to 8 and 9 below, and stayed cold
for weeks. Still, Atlanta's climate is much, much milder than mine, even
though I'm only about 25 miles from downtown.
My point is that to lump all of these into Zone 8 is ludicrous. Zone maps
are supposed to be starting place to determine hardiness. At the least, the
USDA zones should reflect the cold hardiness for the "bread and butter
plants" under average soil/moisture/light conditions, and the Heat Zone map
should do likewise. Or it should give the temperature figures and let the
grower/homeowner/designer pick the plants for the site.
I'm a notorious Zone Pusher in my own garden but normally use rock-solid
plants for my clients. I often suggest "iffy" but worthwhile plants to my
readers, but tell them of the hazards, and how to mitigate them if possible.
I've seen too many gardeners discouraged by bad information. It's time we
took the best available data and put it into a form that's useful!
"A garden, where one may enter in and forget the whole world, cannot be
in a week, nor a month, nor a year; it must be planned for, waited for and
loved into being." Chinese Proverb
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