[b said:
Quote[/b] (vft guy in SJ @ Sep. 18 2006,10:43)]I disagree. You have never given any evidence that cold has anything whatsoever to do with plants initiating dormancy.
I have given lots of evidence...many times..apparently you just wish to ignore it.
here it is again.
Bonsai trees.
Bonsai made from native upstate NY maple trees.
they need to be outside 24/7/365.
they need a very cold western NY winter.
they go dormant exactly the same as any "regular" northern US tree.
A local nursery, several years ago, was selling maple Bonsai trees..
they had them indoors.
they were indoors all spring.
all summer.
all fall.
and into the following winter.
I came across them in January..indoors..not dormant.
they still had their leaves, and looked very sickly.
they were inside a heated greenhouse.
so lets see what happened...
Maple trees indoors vs. Maple trees outdoors.
Maple tree outdoors.
late summer and into autumn.
photoperiod and temps BOTH drop..
tree gets temp and light cues that "its time to begin going dormant"
tree drops its leaves in October..as it should.
by January, in low light and freezing cold, totally dormant.
Maple tree indoors:
late summer and into autumn.
tree is getting a normal decreasing photoperiod, same as outdoor trees, but temp is NOT dropping..
indoor heat comes on in the fall..
tree stays at 70 degrees day and night.
photoperiod is dropping..temp isnt.
In january, the tree is NOT dormant!
it still has its leaves..
conclusion: photoperiod is important, but if temps dont also drop, the plant wont go dormant.
Decreasing photoperiod will NOT cause the plant to go dormant if temps do not also drop.
I personally witnessed that.
now lets take a hypothetical plant..(I did not personally witness this)
Tree is outdoors under bright grow lights.
temps begin to drop in the fall, but LIGHT stays bright and constant.
temps gradually fall below freezing..light levels stay the same..
Will that tree have leaves and be growing in January in Rochester when the temp is 10 below zero, 3 feet of snow on the ground, but lots of bright light is shining on the tree??
unliklely! falling temps will cause the plant to go dormant, even if photoperiod does NOT drop..
VFT's are the same..they are a plant that requires a cool winter to go dormant.
decreasing photoperiod + 70 degrees = not dormant..just weak from lack of light.
bright light + 35 degrees = more dormant. plant wont grow in the cold, even if the light is bright.
less light + cold = ideal..and what VFT's get in the wild and what we should try to provide.
conclusion to all of this?
temp is MORE important than light when it comes to creating and maintaining dormancy.
you can have all the light you want..a VFT at 35 degrees and tons of light will still go dormant, and will be fine in the spring.
a VFT in a dark closet at 90 degrees for three months wont go dormant.
it will just weaken and die.
The same thing happens in the Spring..
leaves on trees dont come out at exactly the same time every year.."breaking of dormancy" can happen within a variable span of three weeks or so every year.
Photoperiod is constant..it does NOT change year to year.
so what causes variabaility?
temp..
trees wont push out new leaves if the temps are still 40 degrees and its snowing..even if the photoperiod is telling them its time. they wait for the warmth, and some years that happens later than other years..even though the photoperiod is not variable..
conclusion?
temp is MORE important that photoperiod when it comes to causing, maintaining, and breaking dormancy.
sorry..I didnt make this up.
I dont undertand why some people are so offended and angry at Nature..but I guess I cant help that.
Scot