ken,

I know that snow protects during winter. What I was getting at was if plants can survive under 4 ft of snow, then it shouldn't bother them to be in a dark location either, should it? It's pretty dark under thick, heavy snow. Not fluffy snow.

After thxgvg everything will be froze solid, I'm thinking middle/end of Oct. to beginning of Nov. but years vary so am keeping an eye on extended forecasts. Averages don't speak for the teens for highs and single digits for lows we experience in mnotw for Nov.

fwiw: Not sure the north side of my house will be the best, there's never any snow for 2-3 ft from the wall and river rock underneath. Its an extended overhang on NS sides. But maybe where I kept my cuttings by the front step would work.

But I have to ask, why tip the pots over?

gg,

I know trees grow in the wild but remember, last year I had -44d almost z2 winter and I think the hemlocks are marginal to z3 so I have to prepare for the worst.

Q: It almost seems contradictory that you say conifer evergreens need light and in you last post, you tell me to cover in the ground pots with a thick layer of mulch. Isn't that keeping them in the dark? What am I missing?

Floral,

Yes, that's exactly what I'm planning to do, keep them outside and protect them. I'm just trying to figure out the best way with the highest survival percentage to do exactly that.

nothing to add...just a very interesting thread.

You cover the pots - not the plants - with mulch!

I believe you tip the pots over to keep them from filling with water on top of frozen soil, Bill. I’m no expert but when I was advised the same that’s what I thought it was for.

ok thanks.

For now, I think I'll wait n see if we get snow early, that would make things a lot easier. I could bury every thing behind the north side my lilac fence and not have to worry about wind, sun, or any winter variables for that matter.

If it snows later, I can rig up a box in the garage. There's a door with decorative glass on the north side, which would let some light in. Then if it snows before the real cold hits, I could move things outside and bury where previously mentioned.

If we don't get much snow at all or the cold comes first, that's another thing. But we'll just have deal with things as they come. At least I have more of a plan now.

I just don't have a decent place to bury pots in the ground. And without snow, that just won't work in z3, too much deep penetration of the cold. Then there's the rodents..... :-|

I know some seedlings are kept in cold storage (and I suspect this means no light). I skimmed the following article. Talks about months of cold storage.

https://agsci.oregonstate.edu/sites/agscid7/files/horticulture/osu-nursery-greenhouse-and-christmas-trees/onn120405.pdf

Keith

Seedlings die all the time around here in the open. They fry and they die.

I didn't read the entire post but if you don't have that many I plant tiny plants in their pot and put them right up against the house on the east side. Need to make sure you pull them out of that location around mid March though as the east sun starts to get warm around that time of year up against the house. The winds on the northside of my house are devastating so only the strong survice in that location. Winds will strip 8" of snow down to the grass.

I had -23, -25 and -26 and no damage to tiny Picea omorika grafts in this location.

Thanks Keith!

I've been reading articles too that say: Conifers have an advantage in needle retention in that they photosynthesize all year, as conditions permit.

And (not a secure site): There is evidence that many conifers, particularly in more moderate climates, can take advantage of winter warm spells and quickly rev up some photosynthesis for brief periods.

There are other very interesting statements (quoted below) made in that last article that lead me to believe photosynthesis becomes next to nil under very cold conditions and that there is also a cost to retaining green needles during this time.

Quote ( of the not secure site ):

Among conifers at higher elevations, leaf photosynthesis in winter seems to be a rarity. In Bristlecone pines in California at an elevation of about 10,000 feet, there was minimal photosynthesis and energy loss far exceeded the little gained through photosynthesis. In fact, it was calculated that it took 117 hours of summer photosynthesis to balance the winter losses of energy. Similar studies of Austrian pines in Europe also indicate that photosynthesis all but shuts down during the coldest winter months.

Needles also exacerbate the problem of desiccation or drying out that occurs throughout the winter. Why then, maintain needles all winter? Why not drop them as the larch tree does?

Even if photosynthesis does not significantly occur in the winter, it does one important thing: it extends the photosynthetic season. In autumn evergreen trees can still be cranking out energy long after deciduous trees have dropped their leaves and they allow the photosynthetic machinery to restart up to two months earlier in the spring.

Revving up photosynthesis early is a decided advantage. In nature, whether plant or animal, survival is all about being able to gather more resources than are lost to the elements. Having several extra months on each end of the growing season more than balances out the costs of being evergreen. It is a strategy that has proven itself through time.

So I'm thinking preventing desiccation is more important than providing sunlight.

I may still have to split these up and put them under different methods of overwintering (maybe) but from what I gather, the little bit of energy the seedlings gain during the cold part of the winter isn't worth worrying about in my climate.

Bill

Thanks whaas!

We have the same problem, probably worse, with the winter burning on certain exposed conifers.

Out in the wild, seedlings that have come in previous spring, with roots penetrating into native soil, covered with 3-4" layer of pine needles, dead grass and surrounded by woods, never seem to have a problem. Why? ;-)

Sounds like your east side of the house is similar to what I have so thanks for describing that. We're similar too wind-wise but my warm up/sun time will be more like mid April. :-)

I guess we'll find out.

It looks to be the last half of October before it starts freezing regularly at night. So I'll let the plants harden off outside as long as I can before they go in the cold frame. 17 (small) pots total.

Somewhat wind protected centered on the South side of the house but still get tossed around enough to make them strong.

When I purchased some Bristlecone and Ponderosa pine a few years back the nursery had just brought them out of a steel building that had no windows and everything was crammed in there on pallets, at least 4 months of winter. I would wait as long as possible before storing them.

Thanks wayne!

I was just thinking the same thing. Temps should be near freezing or below, to prevent mold from forming, if I put these in a confined dark place. But I'm keeping my options open.

If we get snow early (recalling the halloween blizzard, with 2 ft. of snow, that remained all winter, several years ago), I'll just bury things in the snow. End of problem.

I made a rodent proof container (cage) to put the pots in. So no matter if things are under the snow or under a mulch pile, I shouldn't have to worry about feeding the wildlife. :-)

yes timing is location specific ...

being covered in snow.. keeps small pots dormant all winter.. sun on small pots will screw everything up ... roots coming active.. tops frozen solid..

will read all above later ...

one other trick.. might be 4 bales of straw .. which might be garbage picked after Halloween ... make a hidey hole.. and stand all your pots in it ... 'add some chopped leaves to cover pots below .... etc ...

as long as vermin are not an issue ...

ken

I'm curious about this too. Last winter, as an experiment, I stored recently rooted cuttings of juniper, boxwood, and inkberry holly in Ziploc bags in the fridge for several months. In the spring I potted them up, moved them outdoors, and they have continued to grow just fine.

That was a long period of zero light, and as recently rooted cuttings I doubt they had much energy stored.

I haven't read all of the linked articles, but here is the chemical equation for photosynthesis: 6CO2 + 6H2O + Light Energy ==> C6H12O6 + 6O2

Water is essential to the process. If the ground is frozen solid, photosynthesis cannot take place as there is no source of liquid water. Similarly, there are lots of trees above the Arctic Circle where there is no sunlight for months at a time.

Therefore, photosynthesis is not necessary (because it can't happen) to keep some plants alive during cold, dark months.

But if that were true of all plants, we wouldn't have cold hardiness zones. Nor are all plants adapted to months of darkness. And what happens when there is light but no water or water and no light? So other factors are clearly at play. However, -40 C is a lot different than 0 C, and if I had to bet, I'd wager that 0 C and complete darkness is unlikely to be fatal for a few months for most conifers.

But it's and easy theory to test!

'But it's an easy theory to test'

I be doing that shortly. ;-)

Just an update:

It's been beautiful late fall weather here, almost too warm (low 60'sf). But they're predicting highs in the low 40's to mid 30's with lows mid 20's to high Teens by middle of next week. I'm thinking that is too cold for exposed pots to remain on the table by the side of the house. And I'll be gone for a week so I won't be here to take action when/if conditions change.

Today I put the pots in their winter containers and surrounded the pots with mulch. I agree with putting them 'in the ground'. I already have a spot dug out so I'll put them there while I'm gone and can check them when I get back. If it stays cold as is forecast, there should be no problem.

I'll air out the cold frame during the day until I leave and by then, winter is supposed to be here.
8 pots in each container: Filled around the pots with mulch.

I might fill around the containers with mulch once in the cold frame but might just cover over the top with mulch. Just depends on if we get a nice blanket of snow before the real cold hits. I'll monitor the weather when I get back and do the least work necessary to do the job. :-)

Cold frame still has some room but I can't think of anything else I want to do this year. So I'll close the lid while I'm gone and hope for the best.

Edit: Of coarse, pictures won't post any more on this site so you'll have to use your imagination. :-/

ETA: dang, got some pics to load using edit.

10-23-19 44d F inside cold frame, early AM. 30d F outside temp. Colder weather coming.

Everything inside the cold frame looked very good when I checked in there today.

The extended forecast predicts high temps only making upper 30's and only for a couple of days this weekend, then the remaining days of November will be below mid 30's to below freezing. The lows will be from teens down to single digits for the whole month. And of coarse, guaranteed colder from then on. So in this shaded location, it will basically stay cold for the rest of the winter.

I covered up everything shown in the last/previous pic with leaves and there's snow predicted on Monday which would be great but even if no snow, the foam-board, bag of mulch and leaf covering should be enough protection for now, until the temps go much colder in December/January/February. The close proximity to the house foundation will help moderate temps and even if we have a snow-less winter, I have additional mulch I can pitch on top but we'll wait and see what the winter brings before I do that. :-)

1" of snow last week with coldest temps so far in the high teens.

Would've been nice to have a sensor inside the cold frame so I could see temps from inside the house.

Last night we received ~10" snow with a brisk east wind. Left us with areas less than 2" deep and places over 24" deep. Dry cold snow. The snow was sparse along the east side of the house but there was a deep drift ~15 ft out, so I shoveled the snow drift over on top of the cold frame, so we have a good foot of the white stuff as additional covering over the door area.

3* f predicted by morning, then highs in the 20's all week. Winter has arrived.

Not much more can be done now, just have to wait 'n see what it looks like after the spring thaw. :-)

Update:

With temperatures rising into the 30's F during the day, I went out to remove some of the snow on the cold frame. So the thawing weather would finish uncovering the CF.

The area of the CF was still under full shade from the fence section, so it could've stayed buried another month no problem. The snow had melted away from the side of the house about 4" or so but was 2 ft deep and partially frozen solid.

After I got the snow down to the bag of mulch, I realized the bag could be lifted off the door no problem and then the foam board too. When I pulled on the door it came right open so guess what? :^)

Yep, brought all the baskets with potted conifers and seed trays into the house.

The container surrounded with the 1/4" screen looked the best, in fact everything inside was fresh and green looking, almost like the day I put them away 4 months ago. Even the tiny Tsuga with 4 needles were still green.

The other 'tote' style container with a plastic lid (some drill holes so perforated) didn't look as good but most of them didn't look so good when I put them in last fall, still the Picea abies, one of the nicer Tsuga seedlings and another small 3-4 needled Tsuga or two came out looking very good.

There's 4 pots, 2 with partially denuded rooted Tsuga cuttings and 2 with Tsuga seedlings that may come from dormant buds again but nbd. I'll see if they come from dormant buds but may discard them eventually.

If I do this again, I won't surround the pots with mulch. It just stayed so wet and seems like the more air circulation the better.

Picea abies:

Tsuga canadensis:

Thuja occidentalis potted cutting:

I'd call the cold frame method a success. And that the one surrounded with hardware cloth did the best overall.

At least I have a way to keep small potted conifers over winter even if I have to cover the area with mulch in a snow-less winter.

So I'm back to baby sitting pots that are under the lights for a couple of months or so. :-)

Even with the four losses, I'll still have more than I can use around my yard. :-)

I don't understand why you brought them into the house? They were happy outside in cool conditions. What is the rationale for changing their treatment?

'They were happy outside. Why fiddle with them?'

I didn't know what to expect.

After more than 4 months, I wasn't sure how much longer they would be able to stay healthy in the dark, damp enclosure. Next time I would not be concerned.

Seedling from last year, brought in from the cold frame.

It went dormant early last season, then broke bud and starting growing late last season, then went dormant for last winter and is breaking bud again. :-)

Picea abies coming to life. :0)

Last update:

Picea abies looking good! :-)

Just wanted to show that everything that came through the winter in the cold frame in good health is actively growing. Been mid 50's and sunny here for a couple of days so been putting the cuttings and seedlings started last year, in the window light for 4-5 hours midday.

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10-14-2020

Instead of a new thread, I'll just add on to this one for the 2020-2021 winter season. After all, one success doesn't mean it always will work, right?

I did everything the same as the previous year, except about a week earlier than last season. A little better looking plants this year. ;-) One Picea mariana seedling, a couple of Tsuga canadensis seedlings, two rooted Taunton yew cuttings, 8 rooted hicksii yew cuttings, one Thuja o. from seed and two Yew seedlings from hicksii seeds sprouted in July. No mulch around the pots this time.

Watered the ground good and made sure all pots had a soaking.

Covered door with sheet of 1-1/2" foam board, one bag of mulch (in the bag still) and raked up the surrounding leaves on top of that. Picture below was October 16th..

Taken today (10-23-20) after 3 separate snow events with accumilation totals of 8-12" and plunging temperatures. Winter has arrived. :-/

The biggest change this year is an installed indoor/outdoor thermometer sensor inside the cold frame, so I can see what the temps do from inside the house.

Today, after consistent 48.5dF since starting, the temp dropped to 45d for the first time. It will also keep track of the warmest and coldest temp during the night (until noon), that way I don't have to rise too early to check on things. :-)

11-7-2020

After winter like conditions during the last week of October, temps in the cold frame went down to a beautiful 40F by Nov. 1st. The 10" of snow cover helped keep it that way.

Now after almost a week of unseasonably high temps in the high 60's to low 70's, the snow is gone and temps steadily rose to 52F today. The bright side is it took all week to gain 12d and the outside temps are predicted to be much colder after tomorrow.

Last season, once it got cold, it stayed cold so we'll see how this pans out.

eta: It hit 55d (11-9-2020) most of yesterday but was back down to 53d this AM and 48 at noon. The NW winds howled all night and the high today is 34F. Lets hope that's the end of that abhorrent warm weather. haha! :-)

11-27-2020

Just for what it's worth. The temp in the cold frame has been almost steady 42.5 F. for the last 3 weeks. No snow to speak of. High temps outside have been low to mid 30's. High temps lately barely above freezing. We'll check for what things do when the cold weather arrives late December/January.

12/15/2020

After near 3 weeks of near constant 40 F inside the Cold Frame, the outside high temps went from above freezing to teens with single digits at night, even -2 one night. The first 30's to began show up inside the cold frame.

The thermometer sensor is on the far side, away from the house, so I'm thinking that's the coldest part of the CF. But so far an ideal temperature for keeping zone hardy conifers over winter and possibly not so zone hardy. We'll see what the rest of winter brings. :-)

1-20-2021

After a month, with inside cold frame temps right around 40dF and not getting any real cold weather to date, we had a few nights of single digit (-3 & -6) below zero. Temps inside the CF went down to 36dF but that's the coldest it's been in there so far this season. The high today outside, went up to 37dF but supposed to dip back into single digits and teens by the end of the week.

This year may not be a true test of this thing but there's still a lot of winter left so stay tuned. :-)

I went out and shoveled more snow over the mound today, bc the snow tends to recede away from the house a few inches (from heat loss I suppose) so I filled in the gap and added a little more snow on top. Should be good again for a while.

2-5-2021

For the last two weeks, temps inside the CF hovered between 37-38dF.

Outside temps have been low 30's for highs and teens to single digits above for lows.

Last night temps went down to Zero F.

Temps inside the CF had been down to 33f at some point, after midnight.

Forecast temps for the next several days are saying down to -20's for a couple of nights with highs of -5'sf for a couple of days. We'll check things then.

I checked the snow cover on the CF today and more snow has drifted in on top so everything looks nice and tight for a good while. :-)

As long as you have them below freezing, you CAN keep them in complete darkness for several months.

Where I work, we harvest and pack tens of thousands of 1gL conifers, put them into large shipping boxes, and store them for shipping. They are in absolute darkness from January through March without any damage. As long as they are below freezing. You can't have fluctuating temperatures going above freezing or they won't last as long.

We have successfully stored, for example, Pinus strobus, in complete darkness at 28 degrees for 5 months.

Brandon, thank you for that information.

Yikes, I never thought about freeze/thaw being problem. My CF is against the house, so possibly could thaw earlier than further out, away from the buildings.

At least with the thermometer, I should have better idea of when it's time to take them out.

Thanks again!

:-)

Thanks Brandon, That confirms my observations from when I was at a nursery to buy plants a few years ago.

Bill,

The problem with freeze thaw cycles is that if the tops of the trees are transpiring, but the roots are frozen, the plant has no ability to replace the nutrients lost. That's primarily why you see winter burn on the south side of many trees in late winter; the tops are respirating, but the roots aren't translocating water or nutrients, or at least not at the necessary rate.

Buildings radiate thermal energy, so the building will cause a slight temperature increase than if you were further away, you're right about that.

Thanks Brandon!

Last year, I took the plants out early (end of Feb?). High temps outside were ~30's & low 40's.

I didn't have a thermometer then but the pots seemed to be frozen and I surmise that the tops were still cold enough to still be dormant. Everything came out fine, so it appears the key here is to go from frozen to thawed, in one fell swoop.

If this works, at least I'll have some way to over winter new cuttings and seedlings. If not, we'll worry about that later. :-)

Just as an side: Last night, outside temps were just below zero. The CF thermometer said 32.4f. This AM, It was -24f outside temperature. I looked at the CF temp and it showed 33.6f. Go figure. :-)

"Just as an side: Last night, outside temps were just below zero. The CF thermometer said 32.4f. This AM, It was -24f outside temperature. I looked at the CF temp and it showed 33.6f. Go figure. :-)"

Everything alive generates a little bit of heat, although photosynthesizing plants are going to absorb more heat than they produce. But even dormant plants have a background rate of metabolism, and I've often wondered how much heat that generates. Not very much, but enough to raise the temperature a degree in an enclosed small space? Probably not. Interesting to think about it, though (at least for me). :-)

Maybe if the CF was heavily packed with plants, I would think that might be possible.

It's more likely, the colder it gets, the more the furnace runs and more heat escapes through the basement walls. Just a theory though. :-)

I'm getting pretty confident that this system will work for all intents and purposes.

After one week of brisk and refreshing (haha) temperatures, with lows in the -20'sf and highs in single digits below zero. Temps inside the CF went below freezing for the first time this season. Coldest it's been in the basement since I've been here.

If this is any indication of what CF low temps are going to do the rest of the winter, that would explain why my conifers came out so nicely preserved last season.

2-18-2021

Over ten days of daytime temperatures never getting above -4F and lows at night near -30F.

The temperature inside the cold frame hit the coldest this season at 29.4F for two days.

So I think the Cold Frame, seeing the coldest part of the winter, has delivered by keeping zone hardy conifers from experiencing temperatures that might be harmful to the root systems. :-)

The outside temps have been going above zero during the day and will be in the 30's by Sunday. Inside CF temp has been over 30F the last couple of days. Let's hope the worst is over. :o)

I'll wait to open the door until just before the temps inside the CF get high enough so the plants break dormancy (nearing 50f). Could be a couple more months yet.

2-26-21

Temps slowly rose during last week, Less than one degree a day.

Outside temperatures barely making low to mid 30'sf during the day, 37 today.

All winter, small changes in the CF temps have been very gradual over several days.

3-22-2021

After temps in the cold frame hovering around 40-42 F for the last couple of weeks, I thought I'd better take a look in case the above freezing temps were conducive for mold spawn.

Turns out, I couldn't tell it's been 5 months and one week since putting my plants away for the winter. Everything looked fresh and green although the Thuja o. was showing it's winter bronze color. Inside all was very moist/wet.

No mulch or anything, just set the plants down on the sandy bottom in their metal trays (to prevent mister night crawler and friends from entering through the pots drain holes). Coldest temp all winter iirc: was 29F.

I closed the door and left the foam board on. The ground is still cold back there so thermometer still shows 42f. I'll leave things in as long as I can (April 14 will be 6 full months).

So now I have a proven way too keep conifers alive & healthy over winter, without concerns about extreme winter temps burning the tops or damaging potted roots.

4-6-2021

Emptied out the cold frame today. Not that the plants couldn't have stayed in there another week or two but our spring weather has been quite mild with 50's & 60'sf and even 75d yesterday. The ten day is predicting cloudy skies and rain with 50's highs with 30's lows. So it's time to let these guys get some sunlight and fresh air.

Tsuga canadensis (seed from the MN state champion tree):

Picea mariana (from seed last season). Thuja o. & Tsuga c. lower part of picture.

Taxus rooted cuttings all look good:

A lot less work than digging pots into the ground and possibly having the rodent problems with exposed plants. :-)

10-22-21

With our night temps going down into the mid to high 20'sf and finding the pots on the grow table frozen solid in the morning, it was time to put things down in the cold frame. It wasn't the cold I was concerned about as much as the pots thawing every day with sunny, highs in the 50's.

/////////////

This most likely will be my last year propagating plants. It's takes quite a bit of my time and with DW retired now too, we want to be free to follow our whims at various times of the year. Life is short.

It's been nine years since we moved into this place with an empty yard and we've populated it with plants pretty much the way we had envisioned.

And I'm getting too old to be starting everything from seed or cuttings.

If I do any more plantings, it will be a few sizable purchased plants but tbh, I've accomplished my interests and ambitions to what can be done here in my zone. Time to move on to the next big thing. ;-)

I want to thank all the good people here for all the help and information given. It's been one of the most interesting, successful and enjoyable ventures of my life. I am blessed.

/////////////

I had to expand the cold frame this summer, expecting success of many cuttings which did not come to fruition. But with receiving replacement plants and purchases made too late to plant in the ground, I still ran a little short on room and have 4 pots that will have to survive in the garage this winter. :-)

This is what things looked like earlier today before the lid(s) were closed (more deciduous plants this time than previous years).

Lid closed, mulch bags and 6"x6" wood with 1-1/2" foam board. I don't think I'll worry about raking leaves this time).

Pots in the garage. At least there shouldn't be the dreaded 'freeze/thaw' problems there would be sitting outside with sun exposure. We'll try it anyways, it's all zone hardy stuff that's no big loss. ;-)

1-7-22

Hello from the frozen north!

The last week or two have been quite frigid.

This morning was -36d F outside and +36d F. inside the cold frame. Remarkable even from my point of view.

The snow cover has been good with over 20" on the ground, even deeper where it drifts around the house (it was over my knees when I walked (trudged) out to get this picture. :^)

For the record.

That map is goofy , it shows 27 at chicago

it's 9 deg @ 12 noon near o'hare

bill .....-37 ooooo mommaduucky

ron, That map may be from several days ago, I was too late to get the one from this AM.. ;-)

Hopefully we've hit the bottom on the real cold for this season, but we can probably still expect some -20's in the mix over the next few weeks.

It limits the kind of gardening I would like to do but it is what it is. :-)

10-18-2022 Update:

Everything came through with flying colors again this spring.

The only problem arose was a lingering winter, that was just warm enough, so that some of the deciduous stuff started coming out of dormancy. But no harm no foul and all I wanted to plant has been in the ground now for a season. I love success!

My plant propagation days are over. We're traveling more and it's become an issue for us to take care of things while we're away. And we all know, good help is hard to find. :^)

I have removed the cold frame, filled in the hole, mulched the soil and will let the daylily's spread over the area. Been fun and educational. Thanks for all the enablement. 8^)

Bill