Chill hours, how much do they matter?

[Richard]

I agree that Redhaven doesn’t work here. It doesn’t work in Homer AK either where there is sufficient chill, mild-enough winter, but way too few degree days in the summer. It also doesn’t work in an ideal location in the hands of an inept gardener. I don’t believe there is a general sense to chill hours, but rather the details should be checked with each and every cultivar.

[alanmercieca]

I have talked to several of those folks. It has never been a chill hour issue but more often a degree-day issue: not enough heat throughout the season in their location for the cultivar they are attempting. Other problems include not enough irrigation because some nurseries advertise them as a drought tolerant plant. The latter is true but underwatering can greatly affect fruit quality. A final problem is under- or lack-of feeding. Again, some of this is due to poor advice from sellers.

Thank you for this information. It makes a lot of sense, I read that too few chill hours = lighter arils and lower quality fruit and that potassium helps rid of that problem, and now that I think about it, it does sound like a nutrient deficiency. I am wondering how come university of Florida does not even know about this. The arils in a taste test of theirs all look very light, and even the Grenada variety there has transparent arils, can you believe that!

[Richard]

Alan, when I consider pomegranates in FL a few things come to mind: native soils (in the panhandle) high in phosphate, a relatively early spring, and high humidity throughout the summer. For the latter I’m not too worried about the fruit – it is hardshelled and there are cultivars with less tendency to crack before ripening. But humidity might enhance disease on stems and leaves. The high phosphate coupled with the early spring is a big worry – just the recipe for the symptoms you describe above. I’d consider growing them in a 25 gallon tub (one plant) then upgrading to a 60 gallon box, using citrus mix that contains washed sand.

[bobinoc]

Isaac, I think you have the right idea about trying a variety of fruits. Assuming you don’t have a commercial expectation, a lot of the fun for people here is trying to grow different things than we can normally get. People on the Forum do amazing things to grow citrus in cold climates. Here in SoCal (Orange County), practically everyone has a citrus tree, so I have all of one citrus and about 40 stone fruit/apple trees. It’s great fun to experiment. Worst case, if you plant something you can’t grow well, just top work over to something else and you’ll have a new tree in no time.

[alanmercieca]

I am not sure if it helps with fruiting, yet I know in hot high humidity climates loamy soil with lots of air is very important it helps to prevent fungus diseases, like a raised bed is helpful.

[Lizzy]

I’m not sure that all high chill apples do just fine in low chill areas. We’ve had threads about it, here’s one:
High Chill Apple in a Low Chill Climate?
On years when we’ve had very little chill, my Gravenstein has done poorly–as in intermittent blossoms throughout the summer and fall, and apples of all stages and sizes, many of which are still undeveloped in winter. And the “blind wood” talked about in the thread.

I think that many of the chill hour ratings for apple trees may be wrong, for the reasons Richard mentions above, which I hadn’t heard before–very interesting, and explains a lot! But this doesn’t mean that chill hours are not important for some cultivars.

[Richard]

this doesn’t mean that chill hours are not important for some cultivars.

Correct. They need to be considered on a case-by-case basis which includes a lot more variables than just climate zone or measured chill hours. As a mentioned above, chill hours were first developed to differentiate between fruit trees that would produce in serious cold winter zones (1100+ chill hours) and milder mid-west zones (700+ chill hours). The extension to lower zones is a well-documented failure.

[Drew51]

you can’t take a 900 hr. chill peach like Redhaven and grow it in some place which receives 250 chill hours.

Ironic but you can take a 250 chill hours peach and grow it in a 900 chill hour location. Not all but I have done just that with the Nectaplum, this year they were exceptional too. Spice Zee needs 200-300 chill hours, but is high chill adaptable. Not really relevant to the conversation just an interesting observation.
Some low chills will flower early here, and won’t work, not so with this one.
The only way for me to know is to try them. I’m going to try a graft of June Pride, looks like a killer peach to me. 500 chill hours, and a late bloomer, it should work just fine.If I can get a graft to take? Patent expired.

[alan]

The usual reason is because they’ve exhausted potash resources in their root zone and nobody has bothered to properly feed them.

Actually, the life span of productivity for peaches is generally considered about 15 years, but there is a great deal of variation between varieties. The longer living ones tend to send up new growth from older wood.

I’ve never considered K to be the main problem with loss of vigor, here it seems to be more about N, H2O and relative drainage- also borer damage. Do you have information I’m not aware of, or is this specific to your region? Wood based mulched trees never suffer from lack of K in my experience.

[Olpea]

I agree that Redhaven doesn’t work here. It doesn’t work in Homer AK either where there is sufficient chill, mild-enough winter, but way too few degree days in the summer. It also doesn’t work in an ideal location in the hands of an inept gardener. I don’t believe there is a general sense to chill hours, but rather the details should be checked with each and every cultivar.

Yes, each cultivar has it’s own chill requirements. What I was trying to communicate is that one has to pay attention to chill hours when it comes to stone fruit (not small variations of taking a low chill peach and growing it in a no chill year but in a larger sense of taking a more typical 800-900 chill peach and trying to grow it in LA, which won’t work).

Of course there a myriad of other factors which may preclude a given peach cultivar from being grown in some locale - degree days, extreme winter lows, soils, etc., but I was trying to offer information relevant to the title of the thread.

Ironic but you can take a 250 chill hours peach and grow it in a 900 chill hour location. Not all but I have done just that with the Nectaplum, this year they were exceptional too.

I agree. It works one way, but not the other. Saturn (the donut peach, not the round one) has a chilling requirement of 200-300 according to DWN, but it does fine here where we get about 1400 chill hours. Strangely, it blooms a little early, but it’s not the first to bloom in my orchard, and tends to be productive even in frosty weather. Galaxy (another low chill cultivar) blooms very early. So early I’ll probably remove it.

[Richard]

the life span of productivity for peaches is generally considered about 15 years,

Perhaps in your environment. I can show you 100+ year-old trees in Redlands-Yucaipa and more in Utah that are producing just fine.

in a larger sense of taking a more typical 800-900 chill peach and trying to grow it in LA

Actually there are areas of the L.A. metropolis with 800-900 chill hours. We have also discovered a few apricot cultivars that were traditionally considered high-chill but producing just fine in areas of moderate (not low) chill in San Diego county.

[Olpea]

Actually there are areas of the L.A. metropolis with 800-900 chill hours.

LA as in Louisiana, where the original poster is from.

[alan]

Not just in my environment, UC Davis repeatedly estimates their productive life span at 15 years- I just did a search and found that estimate on 3 separate sources from them. I have a Madison peach that is still productive at 25 years- still sending out good length annual shoots all along the branches, but others I planted after are gone- my next oldest is about 20.

The sites you mention are not areas known for peach production- it doesn’t surprise me that their are places they live much longer but I suspect those are outliers.

[Richard]

The sites you mention are not areas known for peach production

And yet, 100 years ago Yucaipa and Calimesa were the locus of Peach + Almond production in southern California, as was Beaumont for cherries.

[alan]

Nice places for fruit lovers to retire maybe.

[castanea]

The life span of commercial peaches in the US is very short because growers expect very high productivity and they can only get it for 15-20 years before they burn out their trees. Peach trees in China can be productive for hundreds of years. American growers don’t care because by their standards the Chinese trees are not producing enough fruit each year and of course any fruit produced after you’re dead doesn’t count at all to an American grower. And China is not an outlier.

[Levar]

Here’s a great tool I just found:
http://www.getchill.net/

It calculates chill hour accumulation within a given time frame based on info gathered from wunderground.

And yeah, Miami accumulates 0 chill hours on average lol

[Richard]

Here’s a great tool I just found:

http://www.getchill.net/

It calculates chill hour accumulation within a given time frame based on info gathered from wunderground.

In some populated regions of the world chill hours can vary 50-200 hours every square mile.

[Isaac-1]

Richard, I am sure that is true, but I suspect most of those have either major elevation changes, or they are near a large body of water.

[Levar]

I didn’t know it could be so variable. That’s great to know.
The wunderground map appears to have tons of stations, though. I wonder how effective getchill is for useable data collection.