Highly Variable Chill Hours?

General Fruit Growing
1

Well it is that time again to ponder spring fruit tree planting, and I would like your thoughts on what to select. I live on the 8b/9a line in western Louisiana grow cold hardy citrus, blackberries, blueberries, and over the last couple of years am in the process of replacing some very old dying peach and plum trees.

My problem at this time is proper chill hour selection, the peaches that I have planted so far are rated at between 450-750 chill hours, most being from the LSU peach program.

The problem is our chill hours are highly variable, last year we barely reached 350 chill hours (a 25+ year low), the year before was just over 400. Going over the online records from the nearby agricultural experiment station that closed down in 2011 (under 15 miles away as the crow flies), the recorded chill hours during its last 20 years in operation ranged from a high of 1350, to a low of about 400 with fairly even distribution, giving a mathematical mean of about 570 hours, with about 1/4 of the years surveyed being over 1,000 chill hours. On the various published chill hour maps we are typically shown on the 500 hour line.

Given this variability what sort of strategy would you suggest for a home orchard?

thanks

2

It depends on your spring freeze risk. If it’s low go more with the low chill types. If high go with high chill types. That assumes bloom time is generally later with higher chill.

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3

We typically have our last freeze of the year just before Easter.

4

Isaac:

I don’t know when your trees bloom. Before or after Easter. But more importantly how often have you lost peach crops to spring freezes?

5

I have simuluar situation. Since the climate is changing, I decided to prepare for more spractic winters where chill hours are not met. Thus, I decided to plant low chill only (even if they bloom early). I can at least use preventive measures during late frost events to save fruit but I can’t do anything when chill hours aren’t met.

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6

You could grab a mix of high and low–helping to ensure you get something in both kinds of years.

7

Examine 7-year running averages.

8

Where in Louisiana are you? What types of trees do you want to grow? I may be able to help some.

Drew

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I am in western Louisiana about a eighty miles inland from the coast, as to the running average it is a big spread considering the extremes over the last 7 years has ranged from under 400 to over 1,300 chill hours, so next years 7 year average may be way off from this years, or last years.

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For a mathematician, a seven year running average would have 3 measures in a 22 year period.

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Issac,

The last few winters in the gulf south have been warmer than average. Checking with getchill.net, your area is on track to get more chill this year but there is still a lot of time left so who knows. You already have over 200 hours below 45 though, which is much higher than the previous 2 years at this point during their winters.

I’ll echo @fruitnut though and say that in this region, it’s the late frosts that bite you. In a year like this one, it’s very possible that low chill varieties will meet their chilling requirements early and will be induced to bloom by a long period of temperate weather in late winter, only to suffer damage by a late frost. I’m a few hours southwest of you and my chilling and frost risk is lower here but really low chill varieties in your area would likely experience frost during bloom in many years. This was linked on the forum before and seems like a good guide for bloom stage and cold hardiness: http://msue.anr.msu.edu/uploads/files/PictureTableofFruitFreezeDamageThresholds.pdf

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12

Thanks for posting that chart, it does help some in deciding risk of planting lower hour varieties as we rarely have temperatures below 28F after early March. We also very rarely get down to temperatures low enough to harm early bud formation,winters with temperatures below 20F being a once in every 5-10 year event, and all time record low 13F. Of course even in years like this one with more early chill hours on record may not count for much due to warm streaks like we are currently experiencing with highs in the low 70’s the last couple of days where the grass is already starting to turn green again in places, just in time for a potential Christmas freeze.

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13

I went with a few low chill trees compared to my chill hours (pears(Meadows and Tennousi) and plums(Methley and Santa Rosa).

The rest do not require a certain amount of chill hours that I know of(jujubes, pomegranates, figs, autumn olives, Romeo cherry bush). My area is all over the place with chill hours and last frost dates.

https://etweather.tamu.edu/chill/

This is my first year with things in ground instead of in pots so I’m not really offering up a solution for you, just sharing what I’ve done.

14

Thanks for the TAMU chilling hours link, it is a handy easy reference, the site is about 150 miles northwest of here, so while may not be precise for my chill hours, but should at least provide a handy view at a glance on year to year trends.

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Well it looks like we will be racking up the chill hours here breaking that 380 chill hours we had last year, possibly by a lot, in the next couple of weeks. For the last 3 days, and forecast for the next 4 days calls for lows around 33 and highs around 44 degrees (7x24 = 168 chill hours this week alone), then we have some freezing weather and then back to highs in the 40’s and lows in the 30’s.

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I have taken a wide variety of chill hours due to our varied chill hours. Tropic Snow peach set well last year with a chill hour rating of 200. Gulf Beauty and Gulf rose also set well. My higher chill peaches and plums set poorly, if at all. 3 years ago the higher chill peaches did fine. I liked the taste of Tropic snow and Gulf Rose. Just remember they will be the first to bloom. One problem with the low chill plums will be if you have cold wet weather the week they are blooming the fruit set will be light.-

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