Overwintering Japanese White Pine in Los Angeles, California

liedersinger

Hello,

I acquired a Japanese White Pine earlier this year (purchased through the internet from a New York supplier), only to have my bonsai intructor here in town tell me that no one in Los Angeles has successfully kept this species because of its winter dormancy requirements (must be very, very cold). I was told that I might be able to use my refrigerator (of which I have available space) and adjust the temperature accordingly.

After doing a little research, I think what I need to do is subject the tree to a gradual ramping schedule of placing it (starting when, I don't know) in the refrigerator for longer and longer periods of time until it remains there for 1000 consecutive hours at something above freezing to 35 degrees F., after which a schedule of swapping the tree to the outdoors for increasingly longer periods each day until it can remain outdoors continously and "wake up" again. I think the tree should be watered about once a week during this artificial wintering phase.

Having never done this before, can anyone help me with advice about the foregoing plan and any other observations about keeping this gorgeous little tree alive and well here in L.A, especially during the winter?

regards,
Marc

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Attila

Hi Marc

I have a few Japanese White Pines in my backyard, they came from Vancouver, Canada 3 years ago.
I don't put them in the refrigerator and yet they are still healthy after 3 years. However, this is not a proof yet that they can survive without artificial cold here. Sometimes it takes 5 years for a conifer to slowly deteriorate and die.

There is a Japanese nursery in San Gabriel where I can always find a few JWP for sale. They seem to be healthy.

So, I have hope that with great care they can survive here without using a refridgerator.
My trees grow under shadecloth. Full sun would probably kill them here, but they wouldn't survive in too much shade either. You have find an optimal combination.
It also depends on where in L.A. do you live. There are many micro-climates here, some of them could be adequate for survival, others (like the hot San Fernando Valley) would probably be too extreme for them (btw, I live in the Alhambra area).

During the summer, it is very important to have a very well draining soil. This is more critical here than in the temperate zones because of the extreme heat. Having too much water in the soil will result in slowly "cooking" the roots. Conversely, the air in the soil will act as insulation against the heat, thus keeping the temperature at lower levels.

As far as keeping them in the fridge, I don't have experience doing it, but I am sure the tree would benefit from it.


Regards,
Attila

Emperor Fish

Marc,

Dormancy chill requirements in trees, (at least fruit trees, which is where most of the research has been carried out - for the obvious reasons), is best satisfied through a temperature range of 35F - 55F. Below or above this range and the temperature has no effect, or can even cancel out earlier cold unit accumulation.

I live in the southern UK where we get an average winter temperature of around 5-8 deg Celcius, or around 44F. (I'm calculating this with the little grey cells, so don't pick me up if I'm a degree or two out ). 45F is considered to be the ideal average temperature to achieve cold dormancy requirements, so I must be lucky The hours to satisfy cold requirements are cumulative, rather than consecutive by the way.

I'm not sure that your fridge would be the best place, unless you can set it to 8C or 45F. It all really boils down to what your average winter temperature is. Colder does not necessarily equal better in this scenario.

Good luck,

Fish.

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Bonsainut

Your Sensei is very wise grasshopper. My humble advice would be to sell your white on ebay and buy a black. You will have much less aggravation . Mucho luck to you.

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