So the Eastern Red Cedar in the yard are the winners from these winter thaws we've had this year?

What about root growth? The soil is frozen...but the top inch or so probably thawed out in this thaw, and wouldn't some trees have roots below the frost line?

The basic general pattern for winter is hibernation, with spring being started in a diminished condition due to stored nutrient reserves having been depleted. Spring is the big time for new root growth, followed by a much lower amount in summer. The single biggest time for increased root volume is fall - but this is existing roots stretching out, not new roots being initiated.

Ed, I'd look at it from the other perspective....do evergreens need to respire during winter warm spells? And the answer to that is an unfortunate yes, they do. This isn't at all helpful to the plant, it's not "growing", its just having to undergo cellular respiration because the air temperature went up so high. It's more of a drag on the plant than some helpful phase. Doesn't mean these plants can't manage...they've had to face this forever. But too much mid-winter warmup-in an otherwise cold winter climate-is a stress factor, not a positive thing, for conifers and other evergreens in cold winter zones.

I don't think they grow, but the needles can produce "food" if the temps are high enough. That just means the needles can, on those days, not draw down their reserves but maintain themselves. Notice during the coldest spells the green on conifers "dulls" (losing chlorophyll), but looks better during mild periods.

So the question is...who are the "winners" and "losers" from a winter with a few unseasonably warm spells? I'm sure there are trees that benefit from it, and others that don't. Do conifers or broad-leaf evergreens like holly make enough food to add to their reserves? Or is it a drain on reserves, and deciduous trees that fully hybernate are better off?

What about their reproduction systems...are their any trees that benefit because of how their seeds work, the timing of their blooms, their pollinators? (ie some witch hazel blooms in the winter, a few trees have berries that don't get eaten until winter)

Beng brings up a good point-that of the possibility a given conifer, or evergreen, for purposes of this discussion, could potentially undergo a bit of photosynthesis if air temps go high enough. My own suspicion is that even if this is so, it is more than made up for by the need for respiration, a drain on the system. I highly doubt a good case could be made that there is anything positive about these warmups, so far as "dormant" winter-hardy plants are concerned. I have no proof however.

As to reproductive strategies, the most common, again, among species that are adapted to cold winters, is for there to be a need for "chilling" hours. These needed hours of exposure to cold temperatures, in order that subsequent reproductive systems can proceed, is met by cold periods, not warmups. Again, I highly doubt any case could be made of a positive benefit. In general, what's good for plant species which are adapted to cold winters is for it to get cold and then stay cold. That's the ideal, and every deviation from that is a lessening of conditions, not an enhancement.

Yeah..but in any given area there will be plants from southern regions at the edge of their range, and northern plants at the edge of their range. The requirement for "chilling" is probably going to be met regardless...unless a northern plant at the edge of it's rage requires a REALLY long dormancy.

As far as reproductive strategies...would warm spells lead to more pollinator activity and benefit witch hazel's that bloom in the winter? How does this impact trees with berries that stay on the tree through the winter...I'm assuming those berries serve a function, and a warm spell would impact how fast they got eaten.

My underlying assumption is there are always winners and losers. There are trees adapted to any variation in weather conditions that naturally occurs.

does it matter if their roots are in frozen soil?

one might argue.. regardless of air temps.. soil temps dont fluctuate as much ... especially once frozen ...

ken

Ed, that's what I'm saying. Chilling hours are not a part of this debate. They are being met regardless if it warms up in February. As to benefits, I'd go slow with that line of thought. Most plants do best when they are not "surprised" too much. I can't count how many times I've replied to someone who, upon remarking about some freakish warm spell in the dead of winter, about how "nice" it is, that for the plant life, it's a negative thing, period. Not sure where you're trying to take this, but no, freak warmups are almost never beneficial to the vegetation which exists in a given area, and which is adapted to long, cold winters. Sure sure, maybe in one year, in one location, witchhazel was able to bloom sooner.... or later..... or longer.... than in other years. But this doesn't reflect any general trend or tendency, I don't think.

Truly nothing ever stops, as long as it's alive. Pretty much all trees and shrubs are busy growing roots during the winter (that may be untrue in the frozen north..I've not gardened below zone 5), preparing for a spring ecstacy of top growth.

In my zone witch hazel (H. vernalis) begins bloom in December and continues till maybe March if it's not too warm. Silver maple (A.saccharinum) is just now coming into flower. Elms are probably about on the same schedule (though I haven't had an elm in many years and may be a bit out of sync with them). Everything has it's own cycle, and it doesn't necessarily stop with the advent of freezing weather, nor await warm spring air.

So in conclusion, yes, conifers are growing now.

Here is an article of mine that should clarify under what conditions a tree root will grow in winter. I hope this helps to answer your questions. http://gibneyce.com/8-read-about-follow-up-care.html#Damage

In answer to your question "Where are you trying to take this"? My thought was there are almost always winners and losers from any change...if only because anything that outright kills some trees will create openings in the canopy for others. Whatever the weather is, it is probably similar to the weather somewhere...and with all the exotics, around, chances are someone's yard contains trees from there. Regardless of whether freak warm weather is "good for plants" in general, it is bound to be less bad for some then for others.

Sort of wondering how a couple freakish warm spells in the winter changes the "balance of power" in the forest...what trees are harmed and what plants get an edge. Relevant to the effects of global warming yada yada yada...

I got you...makes sense, because as you say, ther're all these exotic species floating around now. My money would be on the usual suspects-in my world, I always think that whatever has happened, it is favoring buckthorn, lol...since nothing seems to stop that species. Good line of thought.

dbarron, yes, even here, I notice reddish silver maple flower buds swelling (perhaps that's an indication of sap flowing), but not opening yet. Gives hope for the coming spring.