Those Inadequate Hardiness Zones

Prairie Rose

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My zip code is officially zone six, but when I bring up the map and tag my location, I am actually zone five. We see -5 to -10 at least a few days each winter, and occasionally temperatures get much, much worse. The night I was born we saw windchills of -40 degrees, a record that they have only come close to twice since. Alternately, in the summer I have seen weeks triple digits with high humidity.

For spendy plants and trees, I try to plan for the extremes. If I'm going to put that much money and care and investment into a plant, I would hate to lose it because of a once in a decade weather front. If it's not hardy to zone three or four, it gets planted in the most protected spaces I can find.
 

misfitmorgan

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I'm in Zone 5B which is -10 to -15 but I can tell you from experience we regularly get temps down to -20 to -30 on and off for about 2 weeks and three winters ago -37 one day. So I don't understand at all what exactly the hardiness zones are based on. The cold temps here in winter are not a new thing this has been going on the past I dunno 20yrs at least. I will say i have noticed the past 2 winters we have been pretty mild on temps with days in Jan and feb in the 30s-50s and a day in march in the upper 60s. This winter forecast is suppose to be warmer and wetter then "normal" so the trend may continue. Despite the mostly warmer winters we still get those super cold temps in about the first 2 weeks of febuary.

On the Corn topic neither us or my mother got more then 5 mature ears of corn in our gardens in 2015-2018. We have tried several varieties and for some reason it's just not hitting maturity before frost kills the leaves. The exception is last year where it got so very windy in september after raining almost non-stop for 3 weeks, that it knocked over all of our corn. We tried to stand it back up but the ground was to soft and the roots broken on one side. So this year we are going to plant it slightly deeper and put ropes on both side to help brace from wind just in case.

None of our crops seem to suffer much from the cold but they have been there many years already. I will say our rhubarb is odd compared to the kind we had as a kind. It will grow 2 or 3 times in one season. As a kid you had your spring growth then it got hot and killed it and you were done until next year.
 
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misfitmorgan

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USDA zoning is based on a 10 year running average from what I understand. Averages are nice, but a Mean and some standard deviation might be better.

According to the USDA site the zones are based on the average coldest temperature for a 30yr period. The current usda zone maps was published in 2012. But the map is based on info from 1976-2005? That seems really outdated to me and also makes me wonder when they plan on putting a new map out? Really that means the zone map is now almost 15yrs out of date....for a 30yr data range:smack

The previous map was released in 1990 and based on data from 1974-1986..so maybe soon?
 

Dirtmechanic

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According to the USDA site the zones are based on the average coldest temperature for a 30yr period. The current usda zone maps was published in 2012. But the map is based on info from 1976-2005? That seems really outdated to me and also makes me wonder when they plan on putting a new map out? Really that means the zone map is now almost 15yrs out of date....for a 30yr data range:smack

The previous map was released in 1990 and based on data from 1974-1986..so maybe soon?
Ahh tax dollars at work. Now I understand!
 

misfitmorgan

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So I figured out my new lowest average minimum temps for each "winter" month (dec-march) for the past 30yrs at the weather station closest to me....guess what. They need to update their zone maps, I got an average lowest temp of -6.05f which means according to their scale I should be in zone 6A not 5B.
 

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