An important Physiological disease of japanese maple

rockm

Henke,

Dormancy isn't induced by temperature (although it has a small role). Dormancy is brought on by decreasing day length. A tree will not go dormant by only putting it in a colder place in the house.

Trees must be kept outside from late spring to late summer to induce dormancy, or have a way to experience the shorter and shorter daylengths that the summer to autumn transition bring.

Advertisement

ALDEVAUX

Thank you for your comment, Henke. I realise that what I tried to explain in this thread did not create very much interest. My only objective was to try and make bonsaists realise that there are many plant disorders like : temperature stresses, sudden leaf drop, nutients deficiencies, wrong soil composition and pH, excess fertiliser, air pollution, bad watering and many more, that may occur during bonsai cultivation and which plant pathologists have grouped under the name of physiological or abiotic or non parasitic diseases which are quite different from a simple injury or damage.

As for your chinese elm, I have absolutely no experience with that species, but from what I learnt in this forum it is better for them to have a dormant period every year. I suppose that if you have kept your tree under a light period up to now it has not lost all its leaves. Depending how long your winter lasts, I suppose also that you may still have the time to make it dormant by putting it at a temperature around 5 degrees celcius before spring comes. The trees don't have to go freezing to go dormant. I am sure that some more experienced bonsaists in this forum will tell you better than me what you should really do.

I agree with rockm about decreasing day lenght to induce dormancy. here are two other links that will give you more information on the matter.
http://forums.gardenweb.com/forums/...8313519990.html
http://gardenline.usask.ca/misc/dormancy.html

Good luck

Henke

Thank you both! Winter will last until beginning of april. Maybe it's best for the tree if i start converting it to a life outdoors when spring comes and let it induce dormancy in autumn. / Henke

ALDEVAUX

Henke, I think you still have enough time (about 8 weeks) to first get it to dormancy (usually takes a few weeks) and keep it dormant until spring. Just give it less light and cooler temperatures until the leaves shrivel or fall off. Then keep it around 5 degrees celcius minimum in your cold room until danger of heavy frosts prevail outside as spring comes.

rockm

I would not try to induce dormancy with the tree now. Your plan of waiting is a better one. Keep it growing inside. When the danger of frost and freezes have passed, get it outside and leave it there.

If you try to force the plant to go dormant now, you will most likely shock and weaken it. It will drop leaves if exposed to low light and temperatures, but not because it's entering dormancy. It will be a stress induced reaction to a sharp changes in growing conditions.

To enter real dormancy the tree has to have time to do so. This takes longer than a week or two. Outdoors, it takes months. Temperate trees begin their preparations a little after the summer solstice, as the days begin to get shorter. This process is gradual and cumulative. Expecting the plant to do it all in a week or so is unrealistic.

ALDEVAUX

As I said before, I have no experience with either chinese elm or the issue of dormancy.
My advice was based stricly on an article written by Brent Watson who says chinese elm , and I quote:

Maybe I misunderstood what Brent said, but it seems to me chinese
elm has a short dormancy period and this is why I thought that Henke had enough time until april to give his tree dormancy. I have also read some other references where I thought my advise could be right :
http://forums2.gardenweb.com/forums...1454142544.html
http://forums2.gardenweb.com/forums...1142412154.html

Bonsainut

Whoa Ald, you are start as a whip arnt ye? Im off to find me one of those frosty old type fridges. Ma's can kiss my grits if she thinks shes putting leftovers in there.

I liked everthing you said cept, "...I have no experience with either chinese elm or the issue of dormancy."

Lets pretend that wasn't there.

__________________
Keep growing,---'Nut



Lethal Use of Farce

ALDEVAUX

Thanks for the comment, Bonsainut. You should have told me you had some chinese elms that needed dormancy! I would have sent you to Brent's nursery to get one of those old type friges He's the one that is expert in dormancy, not me.

rockm

Alde,

I wonder what Brent thinks about having someone cut and paste his articles on another site...