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Fruit & Orchards

Looking for list of chill hours for apples, etc.

15 years ago

Does anyone know where I can get a list of chill hours for apples? I have found some info on Dave Wilson's website, but those are not the apples I am looking at.

Comments (6)

fruitnut Z7 4500ft SW TX
15 years ago
milehighgirl:

Chill hrs for apples are a rather nebulous factor. Quite a few will grow and fruit with much less chilling than traditionally thought. And if you are talking apples for zone 5b, you can grow any apple with no concern about chilling. I assume you are in the Denver area. That area has twice the chilling needed for any apple.

The Fruitnut
milehighgirl
Original Author
15 years ago
Maybe I'm mistaken then, I was looking for apples with a very high chill hour rate so that they don't break into bloom too early. In Denver we often have warm days followed by a blizzard. So will higher chill hours help to prevent this?
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Sandra: Chill hour requirements aren't set in stone. Especially in a climate like yours the only way to tell for sure is to try. Usually one can get away with higher chilling material than the numbers would indicate. To be fair to the nurseries many factors come into play. They have to list a higher number to limit liability. As they gain experience the number usually comes down, hence more than one estimate. And these low chilling plants that we are talking about are pretty adaptable. There isn't a hard number and certainly not an easily determined number that fits all situations. The timing and quality of the chilling has an effect. Those factors vary widely by location and year. There just isn't a yes or no answer, but many shades of gray.
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Below 45 model: 566 Between 45 and 32 model: 545 Utah model: 522 And, you can probably add about 20 more ch to my equation, as I was late in getting my weather station up and online. Carolyn is describing my situation exactly. My pluots are very late to blossom. All pears are still dormant, but I do finally see a couple of leaves starting to push out this week on a couple of my earlier pears. My Peacotum has only now pushed out 2 blossoms. But, good new for my Minnie Royal and Royal Lee, they are better synced, just took two weeks for the Minnie Royal to really open up the blossoms, and some of the earliest Royal Lee blossoms are turning into little cherries. So, I should have my first decent crop of Minnie Royal/Royal Lee cherries this year. I will be building a netting cage for both of them this year, and am taking extensive measures to keep snails out of my trees this year. They were worse than the birds for ruining my stone fruit. I also had quite a few blossoms on both my pleurries I planted in January, but the danged Burgundy plum was much slower to wake up, so no significant cross pollination occurred, so highly unlikely I'll get any pleurries this year, so disappointed. They are interesting looking trees, though. the leaves are very unique. Patty S.
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Comments (4)
A long time ago, University of Maryland put out a chilling hours map. I have a copy of it on my blog and I put it in the link below. However, like Applenut said, the chilling at a specific location has to do with more factors than any map accounts for. Even a few miles away, might have more or less chilling. I don't use the map for anything other than a general guide when see what other parts of the county average. I prefer to use the local pomology weather station totals to give me an idea on our chilling each year. I only check, so come spring, I know if it will be a good or bad year, rather than be disappointed later on. Contact your local cooperative extension and see if there is a nearby weather station that tracks chilling totals. Although nurseries claim the area I am in is rated around 400 hours, I don't have many plants anymore that need more than 250 chilling units, and that is because in some years 250 is all we get. Here is a link that might be useful: Link to chill hours map
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Thank you for the link you provided, it's extremely useful. I also appreciate you taking time to post to my thread. I have a few other questions. It says to enter the 'start date' for when the chill hours start and the'end date' for when the chill hours end. I am new to Brooksville Florida, so I have no idea what the dates are for when the chill hours start and end here. It doesn't have to be exact, just an idea of what months the chill hours start in, and what month the chill hours end in for the Brooksville FL would suffice. Could you please help me with this? Also there are a ton of different low chill peach trees.....some have a range of 200-250 others have a range of like 250-350....so I have no idea what types of low chill trees would grow best here....what range would be the most suitable for them with chill hours and some are have very low chill requirements, like 100-150 chill hours. So I am not sure whether to pick the higher range (250-350 or 200-250) or the lower range (100-150)
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fruitnut Z7 4500ft SW TX
15 years ago
No, higher chill won't help. You get way too much chilling. Any apple in your climate will be primed and ready to go by Jan or Febr at latest.

But there are apples that bloom later than others. My latest in Amarillo was Rome. But it's not much of an apple. Quite a few nurseries give tables listing relative bloom dates, quite often for pollination purposes. Raintree has such a table in their catalog.

A new apple I'm going to try is supposed to bloom very late. It's called Suncrisp. You can buy and read about it at Adams County Nursery.

The Fruitnut
milehighgirl
Original Author
15 years ago
Wow, I can't believe I was so mistaken. Does this apply also to peaches? I have selected a few very high chill hours peaches for the same reason. I just assumed that high chill also meant late bloom!
fruitnut Z7 4500ft SW TX
15 years ago
milehighgirl:

With stonefruit there is some reason to think that higher chill may help. Certainly you wouldn't want the very low chill cultivars. But the highest chilling peaches and nectarines I've seen are about 1200 hrs. That should help in some areas of Texas where chilling ranges from 100 to 1200+ hrs. But will it help in Denver where you probably have 2000-2400?? Probably not much.

With peaches the approach to avoiding spring frost has mostly been to chose cultivars that are more resistant to low temp at bloom. Two I've grown that fit that bill are Surecrop and Contender. Once made a few peaches with Surecrop after two night in a row of 13F at full bloom.

I'm in an area with ~700 chill hrs. Chill hrs or whatever does have quite an influence on bloom date here. 200 chill hr peaches bloom in Jan or Febr. High chillers in late Febr or early March. But the freezes that get us are usually late March or the first two weeks of April.

Another factor that is involved is the heat requirement a cultivar has after chilling has been satisfied. Grapes have a very low chilling requirement, about 100hrs, but a very high heat requirement to initiate spring growth. As a result they bloom late.

The Fruitnut
myk1
15 years ago
I wouldn't worry about it. You have enough hours to fill any apple and the tree won't instantly burst into flower once it wakes up. It will still look for proper conditions.

Chill hours are a concern for those who don't get enough.

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