JBP in tropical areas

pdbacos

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Hi,

I go back to Maui twice a year to visit my family in Pukalani. The elevation is about 1,500 ft (450 m). On the coldest night of the year, it rarely gets below 60 degrees F (16 degrees C).

About five years ago, I bought several Japanese Black Pines from a hardware store in a town, Kula, at a higher elevation---about 2,000ft (600 m). Occasionally, at higher elevations, they experience frost which is unheard of at my elevation. The difference in climates can be significant, but they are more similar to each other than they are with the climate at sea level. I have a couple of trees in the ground for trunk development, and they seem to be doing well, but I suspect they would probably to better at a higher elevation.

On Maui, at the higher elevation, farmers cultivate fruit trees that one usually associates with chilling requirements alongside of citrus and tropical fruits such as bananas and papayas. You can grow apples, peaches, plums and persimmons at higher elevations, but I'm almost certain, the cultivars varieties have been selected for Hawaii's warmer climate and have lower minimum chilling requirements (fewer chill hours). I'm not sure how "minimum chilling requirement" for fruit trees would translate to "winter dormancy" for pines and deciduous trees. (This past winter, my young mulberry tree went dormant, but it recovered in the spring and put out a nice flush of new leaves and fruit.) At the higher elevation, other mature, deciduous (non-fruiting) trees I have come across include Sweet Gum (Liquidambar) and Japanese Maple (Acer Palmatum). They're uncommon, but I'm not sure if it's because of Hawaii's strict laws regarding the importation of trees, or if it's because so few of those trees survive to maturity.

Looking at Wikipedia, I came across the following:

Trees
Main article: Vernalization

Tree species that have well-developed dormancy needs may be tricked to some degree, but not completely. For instance, if a Japanese Maple (Acer palmatum) is given an "eternal summer" through exposure to additional daylight, it will grow continuously for as long as two years. Eventually, however, a temperate climate plant will automatically go dormant, no matter what environmental conditions it experiences. Deciduous plants will lose their leaves; evergreens will curtail all new growth. Going through an "eternal summer" and the resultant automatic dormancy is stressful to the plant and usually fatal. The fatality rate increases to 100% if the plant does not receive the necessary period of cold temperatures required to break the dormancy. Most plants will require a certain number of hours of "chilling" at temperatures between about 0°C and 10°C to be able to break dormancy (Bewley, Black, 1994).

I think this suggests that it might be possible to grow trees from temperate climates in tropical climates, but that every couple of years they might undergo automatic dormancy that is likely to kill the tree.

I've been trying to find some information on where "Papa" Kaneshiro lived on Oahu. It looks like he lived in Honolulu which is at sea level and has a climate describes as tropical savanna. It's typical lows are 65--75 F (19--24 C). It seems that Kaneshiro would visit Hilo, on the Big Island, where one of Hawaii's first bonsai nurseries was located. Hilo has a tropical rain forest climate with substantial rainfall. Typical mean temperatures range from 71--76 F; it's lowest recorded temperate is 53 F (12 C). The website I came across (http://www.phoenixbonsai.com/days/DaysSepc.html) doesn't mention if the Hilo nurseries propagated Japanese Black Pine specifically, but I think it might be reasonable to guess that they might have. I'm not sure if Kaneshiro provided artificial dormancy for his trees, but I doubt that the Hilo nurseries would have found it practical to provide artificial dormancy for their trees.

I'm not sure this helps you in Australia, but it seems that in Hawaii, it is possible to grow Japanese Black Pines without true winter dormancy: I've not taken any special measures to provide any chill requirements or artificial dormancy, but it may be that my trees would benefit from them. (I suppose I will be able to assess whether maintaining Japanese Black Pines at my location is feasible after another five years.) Looking at "Papa" Kaneshiro's Japanese Black Pines and assuming that those Hilo nurseries propagated Japanese Black Pines, it certainly seems like it might be possible to maintain (reasonably) healthy trees.

Pelarin
 

bonhe

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Wow, big subject! Since we don't see much JBP bonsai in Vietnam, my friends and I are having a plan to grow JBP in Ho Chi Minh City, Vietnam which is a typical tropical country. In Ho Chi Minh City, we don't get winter at all. In the coolest time, the temperature is about 80 F degrees. We just have 2 seasons: 6 month dryness, 6 month rain. At this time, we're trying to propagate JBP from seeds. So far so good!
Bonhe
 

Woody

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Great post pdbacos. It just adds to the evidence that JBPs can be grown in the tropics despite what has been published earlier. With regards to the info about the need for dormancy, once again it shows that this need varies from species to species. I know some members have previously posted their belief that all trees require dormancy, but these members largely come from climates where trees would die without some mechanism to defend themselves against a harsh seasonal climate. It's a bit like why some animal hibernate through winter rather than fight against it. Those from milder climates on the other hand are familar more with trees capable of growing in short cycles year round.

Pdbacos has also suggested further indirect evidence suggesting that JBP grow in Hawaii without the need for special climates, elevations or induced dormancy. I have also since found small posts around on the internet from people in the tropics with trees 5 years and older. One would think that if the need for dormancy was necessary for JBPs, their trees would have died by then. I guess the alternative (assuming no artificial dormancy was induced) is a natural cold spell every few years that would "reset" the dormancy clock if you will. Pretty unlikely however.

I've also been wondering if language is a factor in the lack of information. Perhaps those in tropical countries successfully growing JBPs are less able to communicate their success because English is not their primary language? I've certainly found posts elsewhere in non-English languages which appear to be talking about JBPs but have been unable to translate them.
 

Woody

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Harry It's interesting you state that all JBPs need a dormancy to survive. Interestingly there are threads from a couple of years ago where you participated that clearly had other posters indicate previous success with JBPs growing in tropical climates without harm for 30 years or even more.

I guess you're happy to state your position but aren't happy to actually share in discussions.
 
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