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ellen728(7)December 30, 2007

Hey, y'all! I'm new and happy to find gardenweb and the TN Gardening forum. Question - is Knoxville zone 7a or 7b, and does the distinction matter? I loved digging in the dirt yesterday (12-30) - warm, sunny, and just after a full day of rain. Looks like cold this week, though. I'll have to content myself with peat pots indoors! Any fun ideas for impatient gardeners in winter?

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brandon7 TN_zone(7)

Welcome to the forum Ellen!

Officially, Knoxville is in zone 6b. In the last decade or so, because of changing weather patterns, Knoxville is in the high 7b range (almost 8a). I usually tend to be more conservative with trees (more permanent plants), and plant only zone 7a or colder hardy trees. I wouldn't hesitate to try zone 8a perennials (especially when well mulched).

Now is still a good time to plant woody plants and perennials. If mulched well, they should do great. Also, winter sowing time is coming up for seed planting.

    Bookmark   December 31, 2007 at 8:33AM
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bigorangevol(Nashville)

Hey Ellen we're glad to have you here! Just as an FYI, we have the East Tn Plant Swap and the Middle Tn Plant Swaps in the spring so make sure you check the board for information regarding these.Check out our website at http://www.midtnplantswap.com/.

    Bookmark   December 31, 2007 at 9:51AM
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brandon7 TN_zone(7)

.....and the Knoxville / East Tn Plant Swap website is http://www.easttnplantswap.com/

On our site there's a place to sign up for swap information email, and, closer to the time of the swap, there will be a swap forum to pre-arrange trades. We also try to keep a list of local plant related events up to date, so keep an eye out this comming spring!

Here is a link that might be useful: EastTnPlantSwap

    Bookmark   December 31, 2007 at 11:34AM
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anntn6b(z6b TN)

Welcome, Ellen.
And this is an area of microclimates. I'm about eighteen miles northeast of downtown Knoxville and my bloom on a lot of plants is seven days after Knoxville. Often I'm five degrees colder and the bottom of my hill is five more degrees colder. Wind exposure also affects growing conditions.
Fortunately, last year's drought wasn't our norm.
But the great consistant rainfall of (was it three years ago?) every summer week, isn't our norm, either.
Winter is a good time to start plants here, and get them in the ground before the summer heat hits.
(And last year's bad Easter Freeze isn't the norm, either, thank heavens.)

    Bookmark   January 1, 2008 at 10:23AM
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myrtleoak(z7 TN)

Generally, I would say 7a to be safe (especially north and east Knox Co). If you are near the city or near the lakes (W Knox Co, Farragut, etc.) and Maryville, probably 7b. If you are in the higher elevations, maybe 6b. This is my opinion and some people may disagree with me...

    Bookmark   January 1, 2008 at 3:55PM
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amazindirt(7A mid-TN)

I'm with Ann. This is definitely a region of microclimates. But yes, I do think the general range runs 6b-7b, although there could well be some 6a and even 8a out there. Heck, I've still got live geraniums outside -- in pots. I've mulched them for the big freezes tonight and tomorrow, but they're sacrificial plants for zone research!

    Bookmark   January 1, 2008 at 4:47PM
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brandon7 TN_zone(7)

If you take the official NOAA minimum recorded temperatures in Knox County for the previous 10 years, add them together, and divide by 10, you come up with 11.2 degrees Fahrenheit. This puts Knoxville and Knox County solidly in the 8A hardiness zone. I was off, conservatively, in my post above. I was going by data that I had looked at a few years ago. The average minimum for the last 15 years is 8.2 degrees (hence the high 7B zone range). There will be microclimates that run cooler as well as warmer, but the range for Knox County would probably be 7A-8B.

    Bookmark   January 2, 2008 at 4:03PM
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myrtleoak(z7 TN)

Thus far I have planted for 7B and have yet to have a winter casualty (wish I could say the same for summer!). Quick question: Is there such thing as a digital thermometer-type device that one can purchase that can record the minimum tempoerature each night? Also, I have done the same research as Brandon7 and can testify that his observations are accurate. I think that my means my have been a degree or so different, but there is always room for slight statistical error. Brandon7, did you use data from the Morristown station or the airport? I do agree with the posts about microclimates, however. Here is an interesting analysis of average Jan. highs and lows from the weather channel for Knox area:
Knoxville 47/30
Farragut 46/29
Maryville 46/29
Oak Ridge 46/27
Lenoir City 47/27
Tellico Plains 46/26
Sevierville 46/25
Blaine 45/25
Maynardville 44/23
Norris 44/23
Another important factor to remember is the heat island effect.

    Bookmark   January 6, 2008 at 1:55AM
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amazindirt(7A mid-TN)

Sure, there are many such thermometers. I've even bought them at Walmart. They're called max-min (or sometimes min-max) thermometers.

    Bookmark   January 6, 2008 at 8:19AM
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brandon7 TN_zone(7)

There are actually 7 NOAA substation in Knox Co. (near Broadway/I-640, off John Sevier Hwy, between Middlebrook and Western Ave, Emory Rd at Pelleaux Rd out near Beavercreek Nursery, Tyson McGhee, N Emory Rd in Powell, and Island Home Airport).

I have a thermometer that I built (It was a kit from Radio Shack from back when Radio Shack actually sold interesting electronic things) that has all kinds of neat features. It not only has min/max recording, but also has alarms for over/under temperatures. There are even switch contacts that can be used to control things like heaters, fans, etc. It also does other stuff, but I'd have to find the instruction book to see what they are. I used to use it for my fishtanks.

    Bookmark   January 6, 2008 at 1:01PM
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myrtleoak(z7 TN)

I did not realize that there were seven in Knox Co. Are all of these available online? The only two I was able to find were the airport and Morristown. Is the Broadway station the source of the downtown Knoxville average I stated above (which are slightly warmer than the airport) from the Weather Channel website?

    Bookmark   January 8, 2008 at 2:33AM
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brandon7 TN_zone(7)

I'm pretty sure the data is not available on line, but it does look like it should be with today's technology. NOAA only provides access to the data if you pay it. I had an inside track and didn't have to pay. (-:

I don't know which data the weather channel looks at when they announce average temperatures for Knoxville. The closest substation to downtown would be the Island Home Airport. The one near Broadway would be a little further but would still be near the heart of Knoxville. I don't think of Tyson McGhee as really being "in" Knoxville.

    Bookmark   January 8, 2008 at 11:37AM
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myrtleoak(z7 TN)

Just out of curiosity, which stations posted lower readings?

    Bookmark   January 9, 2008 at 12:18AM
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brandon7 TN_zone(7)

My buddy at NOAA just gave the lowest reading for all Knox County stations for each year from 1990 to present. I was lucky to get that much for free!

    Bookmark   January 9, 2008 at 9:06AM
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ravenman

Good to find a forum like this!
Knoxville was rezoned to 6B due to an anomoly that occurred in January 1985 when the low temperature hit -24 F! That skewed the average low temperature when the rezoning was done. The climate has warmed since then, but you may not want to get too comfortable with the idea of zone 8, as there are many indicators (despite all the global warming hype) that the climate is about to swing back toward cooling. That said, I don't expect -24 again anytime soon.

    Bookmark   January 24, 2008 at 10:04AM
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brandon7 TN_zone(7)

Ravenman,

The hardiness zone map was not likely greatly affected by the 1985 record low. The current official USDA map was drawn up using the average annual lows for 12 years. The record low in '85 only moved the average about 2 degrees (less than 1/5 of a zone). While the zone boarders might have been shifted slightly, the map would still look about the same even without that record low.

I'm not sure where you get the information about the climate swinging back towards cool. Although that would certainly be a wonderful thing, nearly 100% of current science indicates the opposite. The USDA, NOAA, and NASA all predict a definite warming trend in the foreseeable future.

There are basically 3 viewpoints about global warming. Of course many people fall somewhere in between a couple of these.

One extreme viewpoint says that the Earth is rapidly heading for disaster in very short order, and everyone must do anything possible to keep us from going off the cliff. This viewpoint is likely driven by fear and is heightened by lack of understanding. Those that subscribe to this viewpoint may think that everyone else is acting in a suicidal manner.

A middle view points out that the Earth is warming much more rapidly than has been the case in millions of years. This view is solidly backed up by science. The importance of more study and reasonable action where possible is indicated by this viewpoint. Although it is clear that human activity is contributing to Earth's warming, the verdict is still out on exactly how and by how much human activity is causing change.

A third viewpoint claims that the climate is only going through a normal cycle. This viewpoint used to be fairly mainstream especially among some groups, but is now considered a fringe viewpoint with little to no scientific backing. Every day this opinion becomes more isolated as data is collected and analyzed. This viewpoint is likely driven by political and economic agendas. Often those who subscribe to this viewpoint, or the other extreme viewpoint for that matter, simply refuse to accept currently available information.

    Bookmark   January 24, 2008 at 2:35PM
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katiedidcottage(z7 TN / Chattanooga)

Since you all are talking about zones, what is the zone for the Chattanooga area from around Cleveland, Dunlap and right down to the State Line near Georgia?
-Katie

    Bookmark   February 20, 2008 at 4:54PM
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myrtleoak(z7 TN)

What are the indicators and from what site did you obtain your info? One needs to be very discerning regarding the source of information! Global warming is NOT a straight diagonal line. Mant people do not understand this. We may very well see another 5-10 years of slight cooling (a trough), but this trough has to be viewed on a much larger scale. We may see temps go back down to 5-10 for several years here in Knoxville; this must be compared to troughs of around 0 degrees (and occasionally below zero) that were once observed in the region. Eastern weather is particularly problematic due to its frequent fluctuations. In the west, one can usually expect nearly the same minimum for most years. I have viewed a plotting of global temps on a 1,000 year range; it is a zigzagging line that has been continually marching upward. Notice I say "zigzagging".

    Bookmark   February 20, 2008 at 5:50PM
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brandon7 TN_zone(7)

Katie,

Officially, you're in the 7a zone. In the last 10 years, I would guess you have probably been around the 8a range. There is a possibility you've been close to low 8b. I'm basing my guess on extrapolation from Knoxville's data.

Myrtleoak,

I'm not sure what your point is. As has been discussed in other threads here before, our significant change in temperatures here in this region are mostly due to changes in global air current patterns. It is widely believed that this change is due, at least in some part, to global warming, but I know of no proof of this. Global warming has to be examined from a global scale. Our temperature variations locally may or may not be due to global warming, but by themselves can say next to nothing about global warming generally.

You mentioned a zigzag pattern over the last 1000 years. Actually, there are much more noticeable patterns over that time period. And in recent years, temperature rise has been far out of that normal fluctuation. Global warming would be more about the sharp rise at the end of the graph, not the zigzags from year to year or even decade to decade over the past 1000 years.

You are correct about being careful as to where data comes from. Although scientist now have a pretty good idea of what temperatures have been like during the past (at least the last few million years), there are people and organizations out there that purposefully put out misleading information, or withhold information, for political or economic reasons. Probably some of the better sources are organizations like the USDA, NOAA, and NASA. I've studied their data and conclusions probably more than any other sources. I heard an interview with NASA's chief climate scientist the other day, and it was alarming. He was very professional and was careful not to "push the panic button", but after listening to him, there was no doubt that he is seriously concerned about global warming. He stressed that things have to be addressed soon. It's getting harder and harder for the ostriches to ignore what's going on out there. Once the ostriches are brought out into the light, maybe the Chicken Little's can take their eyes away from the sky for a second and everyone can come together to solve the problem in a responsible way.

    Bookmark   February 20, 2008 at 8:42PM
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myrtleoak(z7 TN)

I guess my ramble was not very clear;) I was responding to those who do not view climate on a large enough scale; a slight cooling period does not nullify the overall marked temperature increases observed in recent years.

    Bookmark   February 23, 2008 at 12:36AM
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