A quick question about plant hardiness zones and potential standard deviations (2015, cold)
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How are you using the hardiness zones? I use them as a general guideline. I use trial and error to get empirical data.
I have heard that that the USDA plant hardiness zone map has its limitations in certain areas; I would agree that the plant hardiness zone map should be used just as a general guide, and that plants don’t read hardiness zone maps. I have been tracking annual extreme minimum low temperatures for at least the past 6 or 7 years for the Indianapolis area; I even had a list of several decades of temperature data for Indianapolis at one point, and on that dataset, I rated each winters hardiness zone rating I believe on two separate datasets, one was from about the late 50’s through the early to mid 70’s, and the other one from the mid to late 70’s to the early 2010’s. What I did observe was that the more recent data period had considerably warmer extreme winter minimum temperatures overall. In fact, It appears that the climate changed around 1995, but the winter minimum temperatures didn’t really accelerate until the winter of 1997-1998 onwards. The last time that Indianapolis experienced a low colder than -20F was January 19th, 1994, Which would be classified as a zone 4 winter. Indianapolis has only experienced 6 winters since the winter of 1994/1995 with a low of less than -10 F, including the winter of 2017/2018 so far. This equates to the preliminary calculation which concludes that roughly 25% of the winters since 1994/1995 have been zone 5 in Indianapolis; the rest have been zone 6 or warmer. Prior to the winter of 1994/1995, winters appear to have had considerably more zone 5 and even several zone 4 winters starting from about the early 1970’s through the early 1990’s; I also concluded that the winters in Indianapolis experienced a cycle of milder winters from about the early 1900’s through about the late 1950’s or early 1960’s,which likely explains why the 1960 hardiness zone map also designated Indianapolis as zone 6a.
.... Prior to the winter of 1994/1995, winters appear to have had considerably more zone 5 and even several zone 4 winters starting from about the early 1970’s through the early 1990’s; I also concluded that the winters in Indianapolis experienced a cycle of milder winters from about the early 1900’s through about the late 1950’s or early 1960’s,which likely explains why the 1960 hardiness zone map also designated Indianapolis as zone 6a....
There is a 60 yr cycle in weather that's really obvious to the naked eye when you look at temp history graphs. Your observations confirm that.
The period from 1925 to 1935 was the warmest decade in the 20th century (until the NOAA felt it legitimate to change the raw data.... I'm a Babe Ruth fan. Can I change the record to say he hit 85 HRs in 1927?)... Then it cooled to give us the very cold 60s & early 70s before it started warming again in the 80s & 90s and now we've been cooling off since then (more fudging of the record 3x in the first 17 yrs of the 21st century to make it look warmer. You can look up the history of the ex post facto record changes.)
BTW- there would be no warming in the record at all if the El Nino yrs (unusually warm ocean temps) are eliminated.
There is a 60 yr cycle in weather that's really obvious to the naked eye when you look at temp history graphs. Your observations confirm that.
The period from 1925 to 1935 was the warmest decade in the 20th century (until the NOAA felt it legitimate to change the raw data.... I'm a Babe Ruth fan. Can I change the record to say he hit 85 HRs in 1927?)... Then it cooled to give us the very cold 60s & early 70s before it started warming again in the 80s & 90s and now we've been cooling off since then (more fudging of the record 3x in the first 17 yrs of the 21st century to make it look warmer. You can look up the history of the ex post facto record changes.)
BTW- there would be no warming in the record at all if the El Nino yrs (unusually warm ocean temps) are eliminated.
Our winters have warmed up so much year after year since 1990 and El Nino has nothing to do with it.
USDA maps do not account for local variations which can make a big difference. For instance, I live in a town about 800 feet higher than surrounding areas, enough to make it 3 degrees cooler in the summer, but more interesting, about 7-8 degrees warmer during winter cold snaps (-17 vs -10 last night, for example). This is because cold air, being denser, flows downhill. This can take place on quite a small scale, too. If you live up the hill, your first frost can be weeks after those at the bottom of the hill.
Location matters, especially in winter. A plant that's sheltered by a house will do better in cold weather. There are other forms of protection too, such as partially burying roses, as they do in Minneapolis.
Finally, landscapers and plant retailers often push things that are of borderline hardiness. Why? They're easy to get from growers further south, people like them (more novel?) and they tend to last at least a few years.
Living now in a cold place (NH), I celebrate what we can grow, which is a lot, and leave the borderline hardiness to other adventurers. I experiment with perennials, pushing a zone or so, since they're cheap. But not shrubs, and certainly not trees. Do I miss the colorful azaleas you see in the mid-atlantic? Sure, but other plants, like blueberries, grow like weeds here (well, not quite that bad) and make up for it.
There is a 60 yr cycle in weather that's really obvious to the naked eye when you look at temp history graphs. Your observations confirm that.
The period from 1925 to 1935 was the warmest decade in the 20th century (until the NOAA felt it legitimate to change the raw data.... I'm a Babe Ruth fan. Can I change the record to say he hit 85 HRs in 1927?)... Then it cooled to give us the very cold 60s & early 70s before it started warming again in the 80s & 90s and now we've been cooling off since then (more fudging of the record 3x in the first 17 yrs of the 21st century to make it look warmer. You can look up the history of the ex post facto record changes.)
BTW- there would be no warming in the record at all if the El Nino yrs (unusually warm ocean temps) are eliminated.
My family's farm journal from the 19th century showed no maple sap runs for sugaring until March if they were lucky. Ever. Now the same area where the farm was sap is being collected in January or February almost every year. Just one example for you. 1933 holds the record low temperature for New England. -50 air temperature in Bloomfield, VT that year.
Getting back to the topic here the zones should be taken as a general guideline. My place can have as much as 10 degrees difference in temperature from the village where the NWS collects data. The village can have a frost and I will not. 5 miles can make a big difference sometimes.
There is a 60 yr cycle in weather that's really obvious to the naked eye when you look at temp history graphs. Your observations confirm that.
The period from 1925 to 1935 was the warmest decade in the 20th century (until the NOAA felt it legitimate to change the raw data.... I'm a Babe Ruth fan. Can I change the record to say he hit 85 HRs in 1927?)... Then it cooled to give us the very cold 60s & early 70s before it started warming again in the 80s & 90s and now we've been cooling off since then (more fudging of the record 3x in the first 17 yrs of the 21st century to make it look warmer. You can look up the history of the ex post facto record changes.)
BTW- there would be no warming in the record at all if the El Nino yrs (unusually warm ocean temps) are eliminated.
I too, concur with you that weather patterns go through cycles and fluctuations over periods of time. I just read a blog by a gardener by the name of Jack Falkner. He posted a blog back in 2014(September or October of 2014 IIRC), and he plotted minimum winter temperature graphs which span the time from 1962 through 2014; I essentially went back and just read that dated blog this evening and looked at the temperature graph for Indianapolis from the years 1962-2014. What I have found was that the temperature dataset from 1962-1963 through 1993-1994 featured 15 winters which registered as either a zone 5 or zone 4 style winter, since 1994/1995, thus far there have been only 6 winters designated, including this winter thus far as being colder than zone 6(extreme minimum of -5 F to -10 F)the lowest two temperatures this winter so far in Indianapolis have been -10 F and -12 F(Zone 5b), the winters of 1995-1996 and 1996-1997, as well as 2003-2004 and 2008-2009 were also zone 5b, while 2013-2014 registered as on the border of zones 5a and 5b(-15 F and -14 F were the coldest lows that winter had respectively. There have been No zone 4 winters(temperatures of -20 F or colder since the historic arctic outbreak of 1993-1994), so..........unless this winter gets down to -20 F or colder, which remains to be determined, then Indianapolis(the city limits in Marion County at least)could well be in the offing of going 24 years or more without having another super frigid outbreak of cold air, a.k.a a zone 4 winter -20 F or colder. Whereas the period from 1962 to early 1994 featured like 7 winter seasons with a zone 4 designation.
Last edited by Isleofpalms85; 01-07-2018 at 07:48 PM..
I think the USDA zone map shows the *average* minimum low temps. So in any given year the minimum low temp is likely to fall within the zone's range.
But the zone map doesn't include the extremes, the all-time minimum lows for an area. That gives you more of an idea how low it potentially can go.
In the places I have lived, generally the extreme lows were actually 1-2 zones colder.
Right, average minimum low temps over 30 years. Latest map is based on data from 1976-2005.
In most cases, I would imagine that your average lows now won't be as low as those represented by this data.
If there are more specific maps for micro environments within a region available to you, that's even better.
Certainly in my neck of the woods there's a huge difference between winter low temps where the weather station is located and the area where I live.
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