Japanese Maples Chill Hour Requirements

[Gustavo Martins]

Interesting. Does the tree go through a proper dormant cycle every year?

Tipically It looses leaves in late December and leafs out in February. As far as I remember, this year’s winter was really warm and I don’t remember seeing the temperature getting lower than 10 C. It leafed out the same and strong. Pushing its second push of growth so far

 

[Clicio]

I only got one Japanese maple, but so far so good. It’s been 4 years now. Zone 11. Minimal chill hours for sure.

Same here, @Gustavo Martins .
Zone 11a, São Paulo. I've got a Deshojo, a couple of JM Palmatum and a Kotohime.
All doing good. I don't worry about winters (they do go dormant here), but summer is a concern. Even being very wet, sun scorch is indeed a problem for maples. So...
In the shade they go.

 

[Gustavo Martins]

Same here, @Gustavo Martins .
Zone 11a, São Paulo. I've got a Deshojo, a couple of JM Palmatum and a Kotohime.
All doing good. I don't worry about winters (they do go dormant here), but summer is a concern. Even being very wet, sun scorch is indeed a problem for maples. So...
In the shade they go.

Yeah mine goes into a more shady position when temperatures start hitting the 24C mark.

 

[Weaponman]

Here's an interesting website that shows chill hours by area: http://agroclimate.org/tools/chill-hours-calculator/

I know Japanese maples are sold as far down as Ocala, and have read posts on this forum of a guy claiming to know of some old Japanese maples thriving a bit north of Orlando. Somewhere around 150-200 chill hours seems to be the lower limit of the species.

I’m in Orlando and have been maintaining an orangeola for 3 years. It stays in full shade and get a kiss of screened sunlight in afternoon. I just ordered a few dwarfs and another cultivar that had anecdotal heat tolerance. If they can breed low chill peaches at the university, certainly we can get a Florida adapted acer palmatum cultivar.

 

[Katie0317]

Super interesting topic. I've also searched this as I am fascinated with the idea of breeding a Japanese maple cultivar that can thrive in zones 9 and above. There's more research on this topic within commercial fruiting plants such as peaches, thats probably where the money is.

I think a good method for conducting research would be to collect as many Japanese maple cultivars as possible, then propagate maybe 2-10 cuttings from each cultivar. From there, keep them in a temperature controlled environment with a fixed number of chill hours per year and record which cultivars do best under N chill hours.

From there, start crossing maples that have the most promising traits for low chill requirement, heat tolerance, and any additional traits that may be beneficial such as growth speed, vigor or attractiveness. I've read that plants grown from seed have a range of chill requirements that averages out to be equal to the mother plant. So it is possible to select for the lowest chill requirement seedlings over generations.

sorry to share that Tampa is too far south to grow maples of any kind. About 15 to 20 miles south of Orlando would be stretching it. Mostly it's the heat. I have to move mine around in the summer.

 

[Weaponman]

I dunno. Given how many hundreds of years that thousands upon thousands of people have been cultivating Japanese maples on every continent, and how there are now more than 1000 recognized cultivars, the notion that you're going to think of something that hasn't been thought of before comes across as slightly naive.

Thousands of people have been cultivating them

Tipically It looses leaves in late December and leafs out in February. As far as I remember, this year’s winter was really warm and I don’t remember seeing the temperature getting lower than 10 C. It leafed out the same and strong. Pushing its second push of growth so far

mine keep leaves until early December and usually stays dormant until mid March

 

[Weaponman]

sorry to share that Tampa is too far south to grow maples of any kind. About 15 to 20 miles south of Orlando would be stretching it. Mostly it's the heat. I have to move mine around in the summer.

Red maples should be fine in Tampa

 

[Katie0317]

There's a big bonsai store just N of Tampa called Artisans. Talk to them about it and you'll get the facts. They won't grow there.

 

[Weaponman]

sorry to share that Tampa is too far south to grow maples of any kind. About 15 to 20 miles south of Orlando would be stretching it. Mostly it's the heat. I have to move mine around in the summer.

Red maples should be fine in Tampa

There's a big bonsai store just N of Tampa called Artisans. Talk to them about it and you'll get the facts. They won't grow there.

I’ve been there last year. The guy had a bunch of massive collected red maples in water tubs…….

 

[Weaponman]

Red maples should be fine in Tampa

I’ve been there last year. The guy had a bunch of massive collected red maples in water tubs…….

Speaking of read maples, here’s the one I’ve been working with for a few years

 

[Katie0317]

Red maples should be fine in Tampa

I’ve been there last year. The guy had a bunch of massive collected red maples in water tubs…….

The owner Joe took on a partner recently. I only saw a vast number of jade plants in water tubs the last time we were there. No maples and Joe had said they wouldn't grow there as have a number of people who've tried.
Yours is looking good. You're keeping it in a lot of shade...? Makes me want to try one. Did you buy it in Orlando? I'm in Winter Park. There are a few plant shops nearby that have bonsai but the prices are comical.
Where do you buy your trees?

 

[dbonsaiw]

Always cool to see JMs growing in Brazil. Do the folks in hotter climates find that the JMs weaken at all over time due to the shorter dormancy period or do they not skip a beat?

 

[ChefB]

Is it possible that Japanese maple dormancy is triggered by day length and/or temperature? It seems to me that the zones that can’t grow Japanese maple have issues with sun scorching and if your plant is containerized and can be moved or kept shaded you can have success in a hotter climate. São Paulo rarely drops below 49°F but his tree goes dormant. December in São Paulo is when day length begins to decrease. Is there a relationship there?

 

[dbonsaiw]

Is it possible that Japanese maple dormancy is triggered by day length and/or temperature?

Hit the nail on the head. As the days get shorter and it gets colder, the deciduous trees realize they need to prepare for winter and go dormant. Sao Paulo is paradise, but the areas where these trees are native experience harsher winters that require dormancy for the tree to make it through the cold.

 

[Clicio]

Always cool to see JMs growing in Brazil. Do the folks in hotter climates find that the JMs weaken at all over time due to the shorter dormancy period or do they not skip a beat?

Not here, under shade.
Today it is the beginning of the Autumn and all my maples - and now I have many different cultivars - are doing very well.
Trident maples don't skip a beat; Kotohime, Kiyohime, Orange Dream, Palmatum and Deshojo are stronger every year.
I guess Tampa is not much hotter than São Paulo - but my house is higher than São Paulo, by the mountains.
It's been working OK with my climate.

 

[Cadillactaste]

I only got one Japanese maple, but so far so good. It’s been 4 years now. Zone 11. Minimal chill hours for sure.

Puzzling...since Japanese maples can't be grown in south Florida. They have zone envy because of this.

Are you sure...you are a zone 11?

 

[Cadillactaste]

Same here, @Gustavo Martins .
Zone 11a, São Paulo. I've got a Deshojo, a couple of JM Palmatum and a Kotohime.
All doing good. I don't worry about winters (they do go dormant here), but summer is a concern. Even being very wet, sun scorch is indeed a problem for maples. So...
In the shade they go.

Really peculiar ... zone 11. I wonder why southern Florida with all their bonsai knowledge. Can't grow them.

My next question...how many years have they wintered there? And also do they grow in landscape settings as well?

 

[Fidur]

I have had two palmatum for the last 2 years. They get dormancy about late december and come back in March.
In my climate, I have zero chill hours.... (this year for the very first time, we hit the 45ºF for some hours)
A grower 5 km from my home have had palmatums for at least the last 20 years.
So I guess dormancy comes with day lenght more than with temperature...

 

[ChefB]

Anybody hear the one about the Florida man who tried to grow a Japanese maple?

 

[Clicio]

Kiyohime under shade, Brazil.



Laceleaf Maple under shade.