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.
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.