They flower and set fruits that rot from heat and humidity before ripening. Notice that many near-tropic and tropical fruits have protective skins: avocado, banana, citrus, pouteria to name a few.
It was established 20 years ago by a member here (applenut) in Riverside CA.
That’s pretty clear. It certainly is observed the amount of flowering and the duration of the bloom seems to be tied to those chill hours quoted everywhere, but the ability for a certain variety to handle the overall conditions in a warmer climate is and successfully germinate and hold the fruit is the issue.
Thanks
This is false for apples. However, nurseries are very shy about changing their spiel (even when they know it’s wrong) for a number of reasons.
I suspect it is also true for pears but my experiences have not been as inclusive as applenut. He is now helping locals farm apples in equatorial Africa.
I’ve been steering away from cider apples because they all seem to be higher chill than my area.
I wonder if I will find one with FB resistance
Since I will be buying some scions this winter anyway, I may grab a few of the better reviewed pears that I thought were just beyond my area’s reach and give the idea a go.
Certainly a cheap way to experiment.
Summarizing the information contained here is far more difficult than it appears. Many of these old fruit breeding programs have varieties never released or missing. Much of the information gets lost to time without websites like growingfruit.org…This was the previous attempt at breeding pears in Canada Canadian Pears Enie, Menie, Miney, Moe, Phileson, Sauvignac,
Not surprised at all. Considering this is how evolution works giving most open pollinated fruit genetics that differ a bit from their parentage to enable successful ones to be naturally selected.
There are certainly tens of thousands of varieties of apple, plum, cherry, etc. In the world counting both domesticated and wild.
Just for the domesticated ones (which I am referring to as human maintained varieties and bred varieties) there is certain to be way too much information to easily find.
Complicating things is of course the fact that most of the information comes from the commercial field (rightly so) at select spots on the globe which are most certainly NOT my backyard or within many hundreds of mea of it.
This is a great forum
I may not understand what you’re saying, but I don’t think it’s false for apples everywhere. California is a different winter than many other places with the same number of chill hours. What’s different is the variation in temperatures. California has very consistent winter temperatures compared to here. I’ve studied CA weather a lot. It’s normal for us to have as much variation in temperature in a week as you have in three months in winter.
The Utah chill model gives an inkling of why this matters. That model credits negative chill above 60F and no chilling below 34F. So our average week in winter with a high of 70 and a low of 20 has too many hours above and below the chilling range. A week of 60/30 has much more chilling but both average 45F.
We supposedly get 600-800 hours a year. More than that below 45. Some apples are very unhappy with that. Others couldn’t care less. As a result our bloom period for apples streches over three months. In Amarillo 400 miles north of here with ~1300 hrs below 45 had a bloom period of about one month for 50 apple varieties. In a northern climate with a long cold winter it’s more like two weeks.
Check with applenut. There’s a paper published 20 years ago.
California has 5 different USDA zones and dozens more Sunset zones with viable apple cultivation. Some of them have the steady winter temperature profile you describe but in my experience many others do not.
I have seen so-called low chill apples flower and produce acceptable fruit throughout the Pacific coast states and the entire Colorado/Green River drainage system.
Chill hour models are guestimate systems at best. They have some applicability to Prunus. Ed Laivo has much to say about them.
Just a note on chill calculations. South Louisiana around Mandeville / Covington Louisiana, Zone 9a.
I have a personal weather station. I’m sure I’m not the only one on this forum that does.
I did some calculations for accumulation of chill hours at my home for this past winter.
I used the Utah and Modified Utah method.
The method that subtracts for warmer temps gives me about - 1300 chill hours. Yes that’s right. Negative.
Not using negative numbers for warmer temps gave me around 600 hours of chill.
I used October thru the last week of February as I got blooms then.
Even if I start the clock in November instead, I am still at a - 300+ hour count using the system with negative numbers above 60°.
From how my trees bloomed, or barely bloomed, both in number of flowers and span of time for the flowering, it’s obvious that the ~600 number isn’t right. Weeping Santa Rosa and my unsure of pluot trees I got very few blossoms and they were spread out over 3 or 4 weeks.
At the same time my Flavor Grenade was full of blooms in a tight period. So the ~-1300 number is nonsense as well.
Such is the way of things in my area for winters. Big temperature swings between fronts living next to a warm body of water being the Gulf of Mexico.
One issue I have even trying to calculate using any system is when do you start looking at numbers in the fall? First freeze? First frost? First time temperatures drop to 45° or below? When the tree starts dropping leaves?
How else can you tell when a tree has entered dormancy? Some trees may hold a good deal of leaves through the winter.
On the other end does it stop at bud swell? Bud break?
Again the whole system is geared towards commercial growing areas to help determine trees to choose for any particular area to turn the largest profit.
I’m sure any system you chose doesn’t work for every type of fruit. It doesn’t work for every variety of a particular kind of fruit.
Good times.
At the end of the day we have to see how a particular tree behaves in our setting, regardless of what anyone or any site says about that variety pt fruit tree.
Unfortunately we are being fed the chill hour numbers from the commercial side and the sales side to make choices from.
As I have read in university academic articles and industry articles, tests are done in comercial Orchards typically. Let’s say that particular orchard received 700 chill hours and the variety fruited well. So they publish that number, having no way to tell how much lower the number can be because that is just the weather they had.
I do see notes often on varieties at least stating a less than symbol…i.e. <700 hours. How much less? You have to find out yourself.
That’s due to Ed Laivo’s influence. He’d agree with everything you wrote above.
I spent some time looking at this because nerds like numbers to evaluate before making decisions. If the numbers are only loosely based on hard science they are not nearly as useful.
To finish off my thoughts, I think I will use the first low of 45° or below to start counting.
Why? The tree has spent all summer growing and has sent almost all of its resources (right @Richard? 
) to the roots. I don’t think warm weather works against the accumulation of chill at this time in the trees annually life. The temps have started to cool significantly (here) by that time and that should be enough of a signal that moderate warmth in fall would not add negatively to the total.
Well sure the low chill ones flower anywhere. Things like Honeycrisp or Ashmead’s Kernal, well that’s another story. Goldrush flowers early and easily here in late March and April. Gingergold flowers in April, May, and June, sometimes into July.
The Utah model was developed in Utah for areas with cold winters. It’s not intended for warm climates like south LA or even west Texas. You’re trying to grow fruits way outside the areas they are adapted to. Why is it so hard to understand that they can’t give you a good number for your area?
They aren’t well suited to my area either and I get way more chilling than you do. So I’ve figured out a way to double my outside chill hours in a greenhouse of all places. I heat to 37-40F .at night since our outdoor temps in winter are too cold at night. Then I use shade and evaporative cooling to lower the daytime temperature by 5-15F. That gets me in the perfect range all night and nearly eliminates the above 60F by day.
Not hard to understand at all, but it’s the only tools out there to compare to advertised characteristics for chill hours (some calculation of temperature ands time).
I’m not complaining at all either. I’m just discussing what I see are the reasons it’s difficult to know what may be worth trying to grow for any particular spot.
Each state has an educational institution that publishes information on fruit tree locales and varieties to grow, but for a place with almost no commercial enterprise beyond a bit of citrus they don’t spent the time discussing and updating information on the miriad of choices out there today for someone to grow.
I’d say this forum had been a better tool for understanding the possible choices for me personally than an advertisement from a nursery which may as well be on another planet trying to sell their product.
I’ve learned an awful lot in 15-20 years on the internet. Maybe I’ve also added a few things to the mix.
Anyone that’s selling something can be biased and often are.
Indeed. Can’t sell something that sounds like crap.
Even worse it’s obvious the bulk of online sites use the exact same description of the tree and fruit.
Not surprising as they aren’t really growers per se. They are middle folks that perhaps only host the trees for a season or so from somewhere to somewhere else.
Here in the forum we get honest feedback of individuals opinion of a fruit and it’s great to know we have different palates and taste buds as well.
No, for the most part the roots develop resources from nutrients in the soil.
This is a good plan. Even if you were to start 10/1 and the 1st sub 45° temperature was 10/25 the outcome would be the same.
I recommend you only count a contiguous hour at or below 45° and any part thereafter. So a contiguous low of only 40 minutes wouldn’t be included in your total. But a contiguous low period of 4.3 hours would add 4.3 hours to your total.
For my Prunus I consider 10/1 to 4/1.
I was referring to the gamut of M. domestica cultivars.
It’s fun to play with numbers.
My station records conditions every 5 minutes. I just do a lookup based on the temp criteria and return a value that I sum, so I’m not rounding up to an hour from a fraction. There may be nights that barely touch 45, but I think they are pretty infrequent.
Regardless there is no magic with the 45° temperature. It’s not as though the tree can differentiate slightly above or below. It should be close enough knowing it’s all a bit of a crap shoot anyway.
That on the whole tree resources being generated and stored in the roots. I guess it would be better to say the tree stops sending those resources up into the above ground tree at some point in the fall or early winter?
I have no schooling in botany so… Should get a book though.
One was recommended to me by the horticulturalist at Raintree.
Coppice Agroforestry, by Mark Krawczyk.