Growing Malus/Prunus In Hotter Zones

[electronfusion]

To start off, I like to force things sometimes, even if it means much more effort in the long run. So rather than asking what I should be trying to grow where I live, I'm only asking advice about the how. I have lots of tropicals that live outside in summer and come inside under grow lights in the winter, and seem for the most part to have stayed healthy and fruiting through several years of this. But growing colder climate trees in a warmer climate seems trickier.

Most of the common apple and cherry cultivars seem to require extensive chill hours. Some, like Anna Apples, have lower chill requirements. For some cultivars, information varies by the source. The nurseries here sell many trees that sources online say need more chill than we actually get here, yet those trees seem to look healthy at the nursery. And for some cultivars, the descriptions only specify USDA zones. But it sounds like two areas within the same USDA zone might have the same minimum winter temperatures, while one area stays colder longer than the other, and one area gets hotter summers than the other. How does one tell whether it's the hot summers or the chill hours that a cultivar needs to thrive, or both? I'm hoping there are some reliable rules of thumb.

Has anyone tried binging heat sensitive trees inside under grow lights during the hottest parts of summer, so they can continue growing, and putting them back outside for the cold months? Or does a shade cloth work better? My intuition says shade cloth wouldn't reduce temperature much when the ambient temperature is very high.

Has anyone tried using chemicals to induce dormancy when temperatures aren't enough? This article suggests it's possible ( https://www.actahort.org/books/49/49_14.htm ), but the majority of it is behind a pay wall, and I can't find much else on the topic. Web search results seem dominated by people trying to sell apple trees in central Africa.

 

[Wires_Guy_wires]

I have done chemical dormancies and you do not want to go there, not at all.
One miscalculation and they're dormant for a decade, or worse; somewhere in between dormancy and growth for a decade. If you don't have lab results on the specific cultivar, then don't. Or do your own tests of course, and make the lab results ;-)

It's easier to get a fridge with some weak lights.

I found that most plants can endure just fine being in hotter places than they should. Of course with limits. It's harder to keep tropicals thriving in colder places than they should.

 

[electronfusion]

Oh. Good to know! I'm also wondering whether apples and cherries actually need all those chill hours for general health, or just for flowering and fruiting. Since all of my trees are early in development and will likely be cut back heavily many times over, I sort of expect some years with flowers and some without. Most information I find just sort of assumes that people want a fruit tree primarily for high yields of fruit, so it's hard to separate which advice is relevant.

 

[Leo in N E Illinois]

Every State has a Land Grant University, and an Agriculture Extension Service will operate out of the Land Grant University. Ag Extension Services maintain offices in every county of every state. Contact your local Ag Extension Agent for lists of Malus and Prunus that are adapted to your growing conditions. Granted the Extension Service will be most familiar with commercially significant agricultural varieties, but most apples have beautiful flowers, even if their original use was for fruit production.

Lack of adequate chilling is the reason Prunus and Malus are primarily temperate species. They generally do not do well in sub-tropical environments.

 

[electronfusion]

I have done chemical dormancies and you do not want to go there, not at all.
...
It's easier to get a fridge with some weak lights.

I found that most plants can endure just fine being in hotter places than they should. ...

... chilling is the reason Prunus and Malus are primarily temperate species. ...

Looks like I've found the info I needed from this thread. I'll see how my current cherry and apple trees do through the winter. Both are intended as future shohin, so a fridge for next winter is doable.