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insufficient chill

Posted by CaptainInsano 9b AZ. Sunset 13 (My Page) on
Thu, Feb 6, 14 at 11:47

I am new to growing berries, grapes etc., I have chosen low chill varieties that are rated to my zone 9b. They have made it through the intense summer heat, but now during winter I do not think this year they will receive enough chill. It has been very a very mild winter, most days in the high 60's to high 70's night time low to mid 40's only 3 days dipped under 32. If I am correct chill is between 45 and 32 degrees and negative chill occurs when the temp is over 45 and under 32, take the last 24 hours for example 10 hours under 45, and 14 hours above nothing below 32, that would be no chill correct? It has been the same story all Winter. This 24 hours however, I do not believe will effect my plants as I think they have already broken any dormancy they were in, grapes never fully dropped their leaves, and blackberries did not drop any, they did stop growing however and I have heard that is dormancy also, so I don't know, but they are budding new leaves. I have chosen varieties that are in the 150 to 300 chill range, but I don't think we have received that this year, does this mean no fruit? I have also heard that insufficient chill doesn't always mean no fruit, but that it will shorten the plants usefulness and life. Do I have any hope for fruit this year? I have Kiowa, Osage, Ouachita, and Rosborough Blackberry and Red Flame, Thompson, and Concord grapes. Thanks.


Follow-Up Postings:

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RE: insufficient chill

What city in Arizona and happen to know the elevation of your of your location?


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RE: insufficient chill

"take the last 24 hours for example 10 hours under 45, and 14 hours above nothing below 32, that would be no chill correct?"

Anything above 60 degrees is negative.

This post was edited by Drew51 on Thu, Feb 6, 14 at 12:39


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RE: insufficient chill

Peoria, Az. 85383 Elevation 1142ft, Yeah I was off on the above 68 degree thing, I checked the two closest weather stations to me that report chill hours, which are both about 15 to 20 miles away but are within 150ft same elevation, from Nov. 1st through Jan. 25th 2014 the Greenway station which is closest to me but 100ft higher elevation shows 54 chill hours that is with the total 391 hrs below 45 and 318 above 68, with 15 below 32, that would be 54 total correct? Then the Buckeye station which is 100 ft lower in elevation shows 231 total. So I would be somewhere in the middle I suppose.

This post was edited by CaptainInsano on Thu, Feb 6, 14 at 13:37


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RE: insufficient chill

Am I off on the below 32, being negative as well, The station info shows temp average below 45 below 32 and above 68.


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RE: insufficient chill

Is your area near Peppermill Run?The elevation is almost identical and from11/1/2013 til now,the chill hours are 339.So by Feb.28th that could be close to 400. Brady


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RE: insufficient chill

It would be about 10 miles, is that with removing negative chill.


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RE: insufficient chill

Yes,that total came from using getchill.net.


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RE: insufficient chill

Below 32 are not negative. I think you are going to be fine!
And fyi we hit -14, and then -10 two weeks later, and my blackberry plants still have leaves. They are all brown, and many fell off, but about 50 are still attached.

This post was edited by Drew51 on Thu, Feb 6, 14 at 16:51


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RE: insufficient chill

Thanks for the info I just checked the getchill.net site I found a station a half mile from me, and it only has me to date at 101 on the below 45 model, 81 on the 45 to 32 model, and -55 Utah model not sure exactly what the Utah model includes, but it's not like I can do much about it, I will just have to wait to see if it is going to be enough.


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RE: insufficient chill

Below 32 doesn't count as plus or minus.

Here's a discussion of several models:
http://fruitsandnuts.ucdavis.edu/Weather_Services/chilling_accumulation_models/about_chilling_units/

Here is a link that might be useful: chilling hour models


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RE: insufficient chill

I live in Scottsdale and have successfully grown stone fruit trees with chill requirements of 300-400 hours. We clearly have had that much chill this year and I would ignore the Utah model.


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RE: insufficient chill

I would guess that 81 it is probably good enough for grapes. Most of the ones I have seen are listed at 100 hours. They probably just need a short period to induce dormancy. Not sure about other berries. I wouldn't expect too much the first few years while the plants are getting established. Not necessarily a chilling issue if fruit is absent when the plants are young.

I have only had about 150 hours below 45 in my backyard this year. That is about half of what I get normally. So far all of my Zaiger hybrid trees are blooming and leafing out normally. Pluots, cherries, nectaplum, pluerry.

Dapple dandy pluot is rated at 4-500 and it fruits reliably, is one of my healthiest trees. Sweet treat pluerry is rated at 450 and is breaking dormancy after the first year. It is full of blooms and leafing out normally. Those are the two highest chill trees I have and they don't seem to have a problem with the mild winter.

I get a lot of winter weather in the 45-60 degree range and I am sure a temperature close to 45 is probably good enough. So if I counted say 50 and below I would have a heck of a lot more chill hours. I am -106 with the Utah model this year. That leads me to believe that it isn't valid for areas with mild winters.

This post was edited by econ0003 on Tue, Feb 11, 14 at 16:36


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RE: insufficient chill

  • Posted by fruitnut z7b-8a,4500ft SW TX (My Page) on
    Tue, Feb 11, 14 at 16:37

Utah is worthless for most low chill areas. I've seen numbers as bad as -1,000 hrs around Houston. That would be with about 400-500 hrs below 45. But too many hrs above 60 where chill is negative. Under those conditions pluot and low chill peaches bloom fine. Utah model is suited to cold winter climates, like UT, and fruits that need significant chilling.

This post was edited by fruitnut on Tue, Feb 11, 14 at 17:43


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RE: insufficient chill

It almost seems like there needs to be a model for the southwest. One that takes into account temperatures above 45 without such a negative impact for temperatures above 60.


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RE: insufficient chill

  • Posted by fruitnut z7b-8a,4500ft SW TX (My Page) on
    Tue, Feb 11, 14 at 20:02

Hrs below 45 is what the nurseries use. It's the best for SW from what I've seen.


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RE: insufficient chill

The chill hours listed on various varieties at 45F and below. Even below 32F. From Nov 1 - Feb 28. There is no compensation for temps over 60F.

Generally select trees with estimates of 350 hours or less for good success.

2012-13:

KAZPHOEN156
26th St and Indianola Ave, Phoenix, AZ
Below 45 model: 466
Between 45 and 32 model: 420
Utah model: 382

KAZPHOEN117
Cheery Lynn Historical District, Phoenix, AZ (@ 16th St.)
Below 45 model: 446
Between 45 and 32 model: 425
Utah model: 87

Here is a link that might be useful: Get Chill Hours


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