Hi Ken .There might be some clues in the link provided below

Here is a link that might be useful: Color changes

Or this one:

Here is a link that might be useful: Chemical of the week

from a 1959 article regarding Pinus sylvestris and Christmas tree production:

1. over time, light intensities may bleach chlorophyll pigments

2. low temps that retard chlorophyll formation and may lead to chlorophyll deterioration

3. the initiation of dormancy suppresses photosynthesis which allow photautoxidation of chlorophyll

There was a fourth factor cited, regarding differing responses of the various races and provenances of the species studied to be subject to yellowing.

I know the farther north you go into the adaptable zones of a plant, the more pronounced the winter yellowing becomes. Where I grew up, near the horticultural mecca that is Fargo, it wasn't uncommon to see a planting of Scots pine where half of the planting would be a bright yellow, and White Pine (or whatever is commonly referred to as white pine these days) would mostly be a color ranging from a muddy brown to a limey yellow by the end of the winter. New growth on both would return to the green one expects.

muddy brown to a limey yellow by the end of the winter. New growth on both would return to the green one expects.

Now that I'm in a area where Pinus strobus grows like a weed I see so many (even in sheltered locations) that are limey yellow during the winter (haven't seen any true golds).

Here is an article that comes in from a different angle, looking at what prevents chlorophyll from bleaching.

I have two yellow C. lawsoniana, one in full sun, the other in morning sun only. The full sun is definitely yellower now.

Here is a link that might be useful: evergreen winter

it may sound extremely silly ... but i failed to think along the lines that a needle is a leaf.. and subject to the same fall chemical reactions as leaves in fall .... whats that all about.. lol ...

now i just have to wrap my head around the fact that leaves that are retained ... [as compared to deciduous] .. can change.. and change back ...

i usually relate color change to the death of that leaf .. and it falling off the tree ...

ken

i have a new theory .... debunk it.. or work with it ...

my yellows have gotten significantly more yellow since this post ...

i am wondering.. if the variability of yellow is dependent on how fast it gets too cold ...

i often speak of the suspended animation of ground freeze areas ...

and then someone else mentioned.. that his didnt color well until late winter .. early spring ..

so i am thinking .... that if it gets too cold.. too fast.. the needles do not complete turning yellow due to the suspended animation ..

but if we have a warmer spell .. like i have just had ... then the tree start working enough .. for the color change to continue the yellowing process ...

but when it gets too cold again.. they will stop again.. and perhaps not hit peak until late winter ...

perhaps this could be a reason that some years have great coloration [warmer later into early winter] .. as compared to other years.. when it simple gets cold early.. and they dont have the ability to change any further.. until it starts warming in very late winter.. aka mid march for me ...

it might also explain.. why peeps further south .. who have near my own zone [considering it simply max low temp] .. but dont get ground freeze ... [meaning the trees dont suspend animation] ... get better coloration.. more consistently ...

ken

ps: i am of course, using suspended animation .. rather loosely ... so dont go cryogenic on me .. lol ..

pps: dave.. does your ground freeze???? when to when .... how long????

Here is a link that might be useful: link

so what is your precise question?

Are you referring to the general malaise that can affect certain plants during the winter season?

Or are you referring to the specific characteristics of particular cultivars, ie Pinus strobus Hillside Winter Gold or Pinus mugo Winter Gold?

i was wondering why some years my yellows are winter yellow ... and other years not so much ... or not until spring

and why .. as pix are posted here.. how variable the same cultivar is.. over the various gardens... especially when i noticed some peeps warmer than i.. had better coloration .. which was based on an older post .. where mine were dull.. and others were vivid on basically the same day ... [i should frame that paragraph ... but it runs on so far.. i cant catch it.. lol]

so the question was.. why .. what are the variables that cause the change .. and my last note.. was that i never thought of suspended animation ... as temporarily halting it ..

ken

On this gardening program we have over here, a nurseryman specialising in various Citrus plants was saying that the sunny cold weather he was having was bringing out the best colours on his oranges ,lemons etc. T.

if I was still in college, this just might make an interesting research topic.

You know how certain maples turn red, certain oaks turn red or bronze, etc in the fall when the primary chlorophylls break down.

Without knowing for certain, I would pontificate (even more broadly with a beverage or three), that perhaps the specific cultivars have more of the secondary pigmentation, yet still have some chlorophyll a and b, that degrades when the cooler weather comes, allowing the yellow spectrum to become a little more intense.

And as such, the local weather that year would very much contribute to coloration.

which begs the question...locally, the fall color season was very much unspectacular. Yet the conifers known for winter coloration seem to be much brighter than in years past.

Now if I had another beverage or four, perhaps I could make sense of this...working my way to a six-pack.

yeah.. i like your beer theory .. lol ...

but the problem with the analogy to fall leaf color...

is that many of these turn back to green ...

i think of fall color as a one way street.. with the leaf falling off.. after the leaf dies ...

but a needle can go back and forth ..

so i guess i am asking.. how can it go back and forth ... ???

whats that all about..

presume i just walked in with another 6 pack and some hummus and chips .. and now the discussion 'must' proceed further ...

hope strobi pops back in.. cuz he doesnt allow email ...

where's a grad student when you need one ... lol

ken

The P. sylvestris 'Gold Coin' sitting in my garage gets all day light but no direct sunlight and its still pretty gold.

is its current gold coloration based on where it was mailed from ... what summer and fall was like where it was mailed from .. due to the stresses of its shipping.. the heat in your enclosed garage [cuz yer garage aint outside in WI in january] ... its reduced light inside the garage..

or its genetics???

can you come to any conclusion as to next years color after transplant.. the vagaries of mother nature next summer ... and what she decides to do in fall and winter???

are you offering a conclusion.. or simply a statement of fact????

ken

Well, isn't what effects deciduous leaves/needles is cold nights/mornings with sunny days. The same with conifer bronzing? I assume once the tree has changed, it will not un-yellow until the tree breaks dormacy, so the tree in the garage should stay yellow?

Are Pines the only conifers that yellow? The others seem to go brown orange or rusty orange or kinda purple. Succulents go reddish.

My Sciadopitys verticillata 'Wintergreen' is now almost kinda purple. Only the more exterior needles. A winter purple of the tree would be cool, if somebody found one.

Nah, its an observation I'm throwing out there. Its just interesting that the one in a garage is still gold. There could be many variables as you've eluded to. I don't plan on counting on anything until its in the ground for a few years.

Although this large specimen(could be another gold cultivar) has the exact same gold.

This one was taken in full sunlight (had no choice) so it is washed out as usual with my camera.

{{gwi:628305}}

On a related note...

What is the mechanism that allows certain spruce to have creamy (to one degree or another) or no pigmentation when they break bud but then develop regular coloration as they mature? I'm thinking of certain Picea pungens or any number of Picea abies cultivars.

The most specific information I can find as re: Pines and the onset of winter coloration in specific cultivars references a trigger that involves temperature. As for the exact mechanism...

that requires more libation.

huzzah!