Fruit drop time based on location

[FarmerDan]

I should probably let this alone, but what do I know about what I should and shouldn't do. I have a theory and your welcome to pick at it. Well, I guess I'm not ready to put it down. Let's just say it involves changing spring - frost freeze dates going from southern to northern latitudes. First and last frost dates are tricky. I think when we ask for the typical last or first frost date we get the date when there's a 50-50 chance before or after that date. And then temperature equates to frost how? Anyhow, I had this slug of data from the National Weather Service that is complicated. The "normal" frost date is the average over 30 years. Averages come with deviations, and with deviations come probabilities.

Let me just put this table up here and try to explain it. It's the beginning. Not the end. This slug of date is for NWS COOP ground recording stations. Each comes with a latitude (and a longitude - and an elevation). I don't know where to go from here. Umm, for this example I used the date where, on average, there's only a 30% of a 32-degree temperature after that date. In round terms, every time you jump a 10% probability you add or subtract 5 to 10 days.

My data set has 3,274 stations - points where temperatures were recorded over a 30-year period. I deleted AK and HI.
Then I (well my computer) averaged "last frost dates" at one degree latitude intervals. I know there are problems because I don't know how many stations are in each sample, and I've not controlled for elevation. But, it's Friday and it's after six.

So, I guess I would read the table like this. Selinsgrove, PA, the home of Blue Hill Nursery, is at about 40-degrees north latitude. If my table has any validity, on May 10 there's a 30% probability of a frost. If I'm an apple tree, I like the odds. I'm going to take a swing at western Kentucky, southwestern Kentucky where the latitude is 37-degrees and the average last frost date used here is April 25th, a difference of 15 days.

By the way, figure out your latitude and drop the decimal part. Then, go to the table and find the corresponding whole number - make 37.5896 degrees 37 degrees. Look at that line on the chart. The "frost-free" date on the 37 degree line is the average date for all stations between 37 and 38 degrees.

Based on all the crap above, there must be a pony in here somewhere!

 

[sandbur]

The crab apple timeline thread can give some evidence of drop times for my location. That is why I keep dates on my pictures.

I have been keeping some notes this fall on drop times and ripening times.

Perhaps I can put it together this winter.


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That would be interesting to see. Looking forward to it if you do it.

The problem I see is how to record drop date when some drop for one week and some for four months.


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[Native Hunter]

The problem I see is how to record drop date when some drop for one week and some for four months.


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I think that is what the chart at Blue Hills is doing. You can see when a certain cultivar typically starts dropping and finishes dropping. Some drop for longer periods of time just like you said. I really like that chart. I would like to see something similar for different locations. It looks like I could almost take his chart and adjust it one month to the left and it would work in my area. Maybe that wouldn't be exact, but it would be in the ballpark.

 

[Native Hunter]

I should probably let this alone, but what do I know about what I should and shouldn't do. I have a theory and your welcome to pick at it. Well, I guess I'm not ready to put it down. Let's just say it involves changing spring - frost freeze dates going from southern to northern latitudes. First and last frost dates are tricky. I think when we ask for the typical last or first frost date we get the date when there's a 50-50 chance before or after that date. And then temperature equates to frost how? Anyhow, I had this slug of data from the National Weather Service that is complicated. The "normal" frost date is the average over 30 years. Averages come with deviations, and with deviations come probabilities.

Let me just put this table up here and try to explain it. It's the beginning. Not the end. This slug of date is for NWS COOP ground recording stations. Each comes with a latitude (and a longitude - and an elevation). I don't know where to go from here. Umm, for this example I used the date where, on average, there's only a 30% of a 32-degree temperature after that date. In round terms, every time you jump a 10% probability you add or subtract 5 to 10 days.

My data set has 3,274 stations - points where temperatures were recorded over a 30-year period. I deleted AK and HI.
Then I (well my computer) averaged "last frost dates" at one degree latitude intervals. I know there are problems because I don't know how many stations are in each sample, and I've not controlled for elevation. But, it's Friday and it's after six.

So, I guess I would read the table like this. Selinsgrove, PA, the home of Blue Hill Nursery, is at about 40-degrees north latitude. If my table has any validity, on May 10 there's a 30% probability of a frost. If I'm an apple tree, I like the odds. I'm going to take a swing at western Kentucky, southwestern Kentucky where the latitude is 37-degrees and the average last frost date used here is April 25th, a difference of 15 days.

By the way, figure out your latitude and drop the decimal part. Then, go to the table and find the corresponding whole number - make 37.5896 degrees 37 degrees. Look at that line on the chart. The "frost-free" date on the 37 degree line is the average date for all stations between 37 and 38 degrees.

Based on all the crap above, there must be a pony in here somewhere!
View attachment 26560

Yea, I think the warming in the spring controls when the trees start coming out of dormancy. Then, that controls the fruit cycle. I think you are on the right track here, but as you pointed out, the answer may be a little more complex.....

 

[KyRose]

I have also searched and asked around from time to time on drop times but always came up pretty empty handed. I am excited Blue Hill has a drop time chart on there website and feel it will be accurate for me at my location (within a week or so) As I am only about 200 miles west of his location. As stated though it may vary for others in different parts of the country. Maybe we could somehow create a (drop time chart by location) sticky here where anyone could post there variety and it's drop time.

Seems like I’m a month late on this thread but when you get a certain age most things are like yesterday. I’m like you Wood Duck , I to like the chart that Blue Hill has fixed up, it gives me a view of relative drop times. I know it is relative to his location but I can take it and adjust it for my location or within a ballpark estimate. For example I can compare our Ayers and Keiffer drop dates and figure most everything else for my location, in short I can look at the chart and plan varieties for specific seasons and where I want to plant them.