Cold hardiness: crazy idea?

I have had this idea about cold hardiness floating around in my head for a while and thought it a good time to air it out to see what y'all think of it. Not being formally trained beyond a couple of years at a junior college, it seems logical in it's simplest sense. Usually when things seem logical, they have already been thought of or discovered so I may be 60 years late with my idea. It started last Nov. 12th (birthday trip to myself) as I stood in southern IL admiring the state champ Quercus falcata pagodifolia, thinking how long it had been there. For whatever reason, the memory of reading about the Little Ice Age that occurred in the past few hundred years popped into my head and how this tree probably withstood at least part of it. After thinking and rationalizing for a minute or less, I began scrambling around in the leaves like a squirrel, stuffing my pockets with acorns. Thankfully, I had arrived at daybreak when most sane people were still in bed and as such, my crazed actions were not reported to the authorities. Q. f. pagodifolia had long been on my 'like to try list' but I hadn't given it much thought since it's usually listed as 6a/b at best. I rationalized that if it had withstood some cooler winters of the past in it's youth, it would be more cold hardy than what is typically listed. However, since I have yet to experience the refining influences of the opposite sex, I put the acorns in the garage and forgot about them until late spring. Needless to say, the experiment failed. The idea about cold hardiness sat dormant for a while and then began bouncing around again when I was going through pictures of Baldcypress from the same area for a post here. To narrow my hypothesis down: plants old enough to have weathered some of the colder winters of the 1600's-1850 could possibly be naturally selected cold hardy forms. What is now Zone 6a/b now may have experienced 5a/b temps during the global cooling that occurred in the past. Perhaps this would explain why plants can grow in colder areas than their native range? Sort of a residual genetic heritage. In Dirr's book, he will mention plants growing north of their native range (Leitneria) so perhaps this is another instance. The Little Ice Age was said to have lowered mean temps in North America up to 1.5 degrees Celsius with some exceptionally severe winters. So, what do you think? Already been discussed, of merit or full of bunk? I've attached a picture of the oak with yours truly in front of the oak. Note that I have not yet hypothesized about this oak as my pockets aren't yet full. Also wearing a Mr. Greeley hat from a fine KY thoroughbred farm, Gainesway. The weird look on my face is from arriving to the parking lot at 2 A.M., then sleeping in my truck the rest of the night and from lugging 30 pounds of camera stuff around.

Regards,
Ernie

Has this tree been reproducing naturally in the area around it?

It's funny you guys up north have to worry about cold hardiness, while we in the south have to worry about northern grown trees surviving our heat and humidity. At least with freezing it will get zapped practically overnight, but when they get repeatedly scorched they die a slow and agonizing death.

Escambia,

I didn't take enough time to look around and really take note of what was growing nearby. My memory wants to say that there were some other oaks nearby but I don't remember what kind. I do remember about 1/4-1/2 mile down the trail that there were a bunch more growing and different sizes. Perhaps 2nd or 3rd generation from the tree? Trees don't always completely freeze overnight. Sometimes its a long, slow death of: freeze part of the tree, heal for a year or two, then freeze more, heal a bit, freeze more, etc. Parrotia does this, at least the few plants that we have. What's good for us, is bad for you. I suspect that we will see more ecotype plant introductions in the future to remedy this.

Regards,
Ernie

Hi malusman. Good theory, but other things should be considered before it could be pronounced well baked. One is that the Little Ice Age was neither uniform nor unvarying. That is, although records indicate lots of climatic cooling in Europe and North America, it was not evenly distributed. Cooler weather also brings more snow, so maybe the seedlings/small trees (assuming the tree is at least 200 yrs old, since the cool seems to have had a final peak in the second decade of the 1800s) had better protection.

I think in England the last hurrah! of the cold is generally thought to be about 1815 when the Thames froze last. This co-incided with the time of the volcano eruption that robbed New England of their summer. Crops failed, and my ancestors were forced to migrate to Quebec City for the winter to avoid starvation. My great-grandfather's grandfather wintered in Que. and returned alone. His wife decided to remain in the city rather than face another winter in northern Maine. He returned home and lived with a Malicite/Micmac (American Indian) woman who bore hime 10 children, all males.

Another variable is that the cool was not one long cooling but a series of warming/cooling periods. The unusually cold temps. were interrupted several times with a decade or more of warm spells. Maybe the tree was hatched during one of them and gained resistance to cold as it got bigger.

At any rate, the underlying theory is sound, outlying groups of plants tend to be the ones with resistance to whatever makes them rare.

I've talked extensively with taxonomists and very competent plants people who either live in Southern IL or nearby and have visited the forests of the area and most say that Quercus pagoda(it's been classified as a seperate species for some time now) is quite common in the area and is reproducing naturally.

As for your idea on cold hardiness, it's certainly possible. Some people claim that current natural distributions are largely a result of historic severe cold periods, such as the Little Ice Age. While others argue that current natural distributions are still the effects of the "real" Ice Ages and species haven't had enough time to fully expand their ranges Northward yet.

I think it's likely that many of these trees are still rebounding from the last glacial maximum(about 18,00 ybp(years before present)), and the Little Ice Age might of delayed this or even pushed some of these species back South some. I say this because as recently as about 4,000 ybp there were Colorado Spruce trees (Picea pungens) and White Spruce (Picea glauca) growing over much of Kansas. Now you have to go West 500-600 miles to the higher elevations of Colorado or North 500-600 miles to find either of these species in the wild. Also, most of the current trees in Kansas have moved into the state from the South and SE(most evidence suggest Mexico, Florida and possibly an area of SE Texas or Louisiana were plant refuges during the Ice Ages) in the past 5000 years or so. So it appears that most trees have moved their natural range quite a bit in the past 5,000 years or so, but there is also evidence that some species used to grow farther North than they currently do. The evidence is left primarily in hybrids involving species no longer growing in these more Northerly climates. This is more easily seen in Oaks of the desert SW. There are hybrids involving Shrub Live Oak(Quercus turbinella) in Northern Utah and Northern Colorado, 150-250 miles North of Shrub Live Oak's current native range. There are also hybrids involving Gray Oak (Q. grisea) found in parts of Colorado and Utah, 100-250 miles North of the current range of Gray Oak.

I will say that in some species it seems that their current range is largely limited by where they can successfully reproduce, like escambiaguy might of been thinking, when he asked about natural reproduction of the Q. pagoda in Southern IL. I think Southern Magnolia (Magnolia grandiflora) might be a good example of this. It can be grown in areas about 400 miles North of it's current native range, but it appears that first and second year seedlings can't consistently survive winters much more than 100-200 miles farther North that it's current range.

So, in the end things might be more complex than your theory, but your theory certainly seems to account for some species hardiness. From what information we have about winters during the Little Ice Age in North America, it seems that most of the native trees have endured temperatures at least 10 degrees F (5.6C)colder than what they have experienced during recorded weather observations of the past 125 years. I've found that most trees growing in the wild can be successfully cultivated in areas between 1 1/2 to 2 1/2 usda zones colder.

Hi Ernie,
Great question. One I've considered for a long time. As a collector of plants (not necessarily a devoted zone pusher, however), I've long been intrigued by a real pattern of southern plants that I can grow here in the Midwest. Virtually every plant in America can be pushed a zone north of its current native range. Many can be grown two or even three zones north. I've noted, too, several plants from Formosa, which is zone 8 but for the higher altitudes, which I can grow in zone 6.

I believe there are two reasons for this. One, altitude. Some southern species grow at high, colder altitudes than others, making the transition to growing in northern gardens easy. But this is a really minor factor.

The real reason I think that many, if not all, southern species can be pushed a zone, (or two or three) north is because we had a real ice age only 10,000-12,000 years ago, which, particularly for woody species, is not necessarily all that many generations. (Only twenty generations if a 500 year old oak begats another oak which lives to 500 and begats...) Most probably not enough generations to lose the cold-hardiness they absolutely had to have to survive a climate where glaciers covered everything down the Ohio River and where Florida must have experienced significantly sub-zero (F) temperatures. I can't imagine why the genetics to survive cold would necessarily be lost as quickly as they are not needed.

The mini-ice age, which I believe dipped most of North America at least one zone colder than now, probably only served to reinforce the presence of remnant cold hardiness genetics from the true ice age. Say, where a smattering of Q. falcata pagodafolia bloodlines might have gotten "hardiness" lazy over time and shifted towards zone 7 vulnerability, the mini-ice age probably culled the most zone 7 committed among them from the herd. Result: The entire species is again re-painted with zone 6 colors. Or, at the very least, each provenance within the full Q. falcata pagodifolia range is reinforced with the little extra hardiness it was beginning to lose.

It is really fun thinking about this. Think about Oakleaf Hydrangea, only native to a few tiny sites in the deep south, fully hardy into at least Chicago. Chionanthus pygmea, found in a few tiny locations in central florida, at least zone 6 hardy and maybe zone 5! We are blessed to be able to rescue these plants from a merely southern existence, and to give some of them good northern homes. Just kidding Escambia and Conifer50! But think how less satisfying our northern gardens would be without this vast selection of southern plants.

Someday I would like to "zone out" China, and map out where many Chinese plants' native ranges lie, and see if this one or two zone buffer applies there as well. I would bet it does.

Scott

Hi Scott,

I believe there have been a couple of different attempts at zoning out China. I think I even have one of these maps stuck in a box somewhere, if I find it I'll try to convert it to a digital format. Also, it doesn't appear that most plants in Asia can be pushed as much as plants in North America seem to be able to be pushed. It appears that the Southern expansion of glaciation during the last few Ice Ages didn't extend as far South in East Asia, and also the more mountainous geography of East Asia also appears to have allowed for many more refuges from colder weather and some of the plants that took refuge in these refuges are still "stuck" in them. These plants that are "stuck" do appear to be able to be grown in a couple zones colder than where they are currently native.

Also, much of the interior mountainous parts of Taiwan(Formosa) are more like zone 6, and even some very high altitude zone 5, while part of coastal Taiwan is zone 9/10, so it offers a wide range of zones on such a relatively small island.

Your idea about high altitude certainly applies to many plants from Mexico. There are many higher altitude growing plants in Mexico which have proven hardy to zone 6 in the US. Also, several Chinese plants that are in cultivation in the US come from high elevations of Southern China, which are at similar latitudes to Northern and Central Mexico and South Florida.

And I agree with you, it's really fun and interesting thinking about this.

edited to change slightly my estimate of the mountain's equivalent zone hardiness

This message was edited Dec 12, 2006 6:26 PM

This message was edited Dec 12, 2006 6:27 PM

Hi Kman,

Most of Asia (Siberia included) was never glaciated at all, the climate was either too dry for glaciers to develop even when the temperatures might have been colder, and/or the climate so continental it warmed up enough in the summer to melt the winter snow. But some Asian species are hardier than one might expect from their origin; where Metasequoia grows wild is zone 7/8, but it is hardy to 4/5.

I'd disagree about Taiwan, the treeline species (Abies kawakamii to 3,800m, and Picea morrisonicola a little lower) are only zone 8 hardy. Taiwan is so far south (on the Tropic of Cancer) that there is very little difference between winter and summer daylengths, and therefore also not much annual temperature change either; it is also an island, so doesn't have the continental land area to get cold. The treeline is determined by summer temperature (July mean about 10°C); take off the small annual temperature range, and even at treeline, it isn't very cold there in winter, January mean about 0°C.

Resin

I knew that East Asia wasn't glaciated in the last couple of Ice Ages, but didn't know if it never was or not, so that's why I didn't say it had never been glaciated before. Also, I was only really talking about China and areas Southward, and didn't think about whether Siberia had been glaciated or not. And Metasequoia is one of those "stuck" species that I was thinking about when I added that comment. Then again you could probably argue over when and why Metasequoia got "stuck" and if it was due to that valley area being a refuge during the recent Ice Ages (the ones in the past 1 million years or so) or a refuge at another time.

Also, my comments about Taiwan weren't limited to woody plants, and maybe I shouldn't of used the word "much" of the interior. I was basing my comments on my observations during my visit to Yu Shan national park in Taiwan and it was quite apparent that much of that area saw regular snows and hard frosts(obviously not at lower elevations) and according to locals the area had seen temperatures below 0F(-17.8C) in the mountains(even where trees were growing). Although I can't find any long term temperature records for the higher altitudes of interior Taiwan(nor could I when I was there), only the Yushan weather station(which is well below tree line and near the valley floor) having recorded a temperature of -6C(+21F) within the past 25 years and the Yushan National Park Headquarters(or maybe it was the visitor center, I don't recall for sure) has recorded a temperature of -18.4C(-1F). Although it is interesting that you say the 2 major tree line species aren't more hardy, since some of the flora from much lower altitudes is hardy into zone 6.

Thanks to everyone who responded! I have been rather busy in the last few days wrapping things up before Christmas. I learned quite a bit, including that it is now Q. pagoda, that this has been thought already thought of, trees are still expanding their range from the last big Ice Age and too much more to list. I think that I unwittingly split my question into two seperate ideas, one regarding still existing plants that had lived through the Little Ice Age and also of genetics of southern plants that can grow north of their range because of surviving the last Big Ice Age. I'm rushed for time again but if anyone is interested in discussing this futher, perhaps we could revisit it at a later date. If not, I'll sign off and let it die.

Regards,
Ernie

As a plant person, I am always pusing the buttons, trying to grow plants and especially trying to grow endangered on on the extinct list when I can get them. With plants, it is hard to battle the cold tolerance, because the roots are so shallow. Don't know if this is right or not, but was taught, take care of the roots and the top wil take care of its self. I had a discussion with several professional plant people and aske d them if we gathered the seed and grew it out, wouldn't it eventually be able to devlop to its new climate.

I realize it would still hold all the genetic qualities of where the seed came from, but seems as some of these plants have been able to survive and flurish in od places for generations we should be able to some how grow them.

On a major discussion on another forum we got to taking about the how plants in the south don't survive in the north and visa versa. One person, thinkthey were from New York, instead of looking at the tops of plants, started keeping a record of his soil temperatures at different levels and different times. I was amazed at some of the different temperature flucuations at different depths.

Then I wondered if we created more the root zone eniviroment for these plants and trees that we would have better luck getting them established.

This may sound crazy, but I figured the older trees , probably have well established deep roots and due to their size are able to produce more fiberous roots if needed if the top ones got damaged, but a young seedling is spending most of it's energy between it's canopy and roots. A young seedling is going to be very susceptible to having its root frozen.

Here the really crazy thought. Find some of these old trees and during the winter set up propes to measure the soil temps of the ground around these trees. If say for example the air temp is 20 below, but maybe under the ground is registering at least 32F which would keep the roots alive, or maybe it even at say 45F.

Then the trick would be to create that same heat zone for the roots. I have often wondered if until the trees got big enough, that planting them pot-n-pot over the winter and placing some sort of heat probe into the pot with a thermometer attached to keep that soil warm enough to keep the roots from hitting their cold hardiness limit and dying wouldn't work, until eventually the tree got big enough and deep enough roots to survive on it's own.

I sometimes wonder with these giants, if there wasn't or isn't some sort of faint water table running near or by them that helps to keep the roots from freezing and dying. Seem the water if the soil got cold enough would freeze, but still provide heat.

I do wonder if if not the cold hardiness on top , but below the ground that we need to look at. Too crazy of a thought?

Star, It is common up here in zone 3, yet close to the big lake, to get snow measured for the season in feet rather than inches. They tell me that any depth exceeding nine inches will be enough to take the frost out of the ground. So it is not uncommon to have late Jan/early Feb temps going lower than -30F and under all that snow cover have soil temps above freezing. When walking on snowshoes I have often heard the trees around me "crack" from the cold temps above this cover. You would think that next spring you see fissures in their trunks much like lightening damage, but not so. Woody shrubs like Japanese Kerria (zone 5) will die back to snow depth, yet those branches under will flower on old wood. Ken