Please Help With Cold Frame Ideas

[Deep Sea Diver]

Not sure about the effectiveness of heat cables. Normally the heat is constrained to a discrete area unless there is a conductive bed of material, like moistened pumice to retain the heat and a good thermostat.

If I recall correctly @August44 has used heat cables in his next to the house cold frame, you might PM him on effectiveness.

cheers
DSD sends

 

[hemmy]

If there's room in your garage that's definitely your better option

3-car, last bay is reserved for the separate tropicals and “Mediterraneans” grow spaces. But the shohin will probably go in also. Maybe I’ll split the two big tridents up and my 6yr JBPs, some in, some out.

Thanks All

 

[Paradox]

3-car, last bay is reserved for the separate tropicals and “Mediterraneans” grow spaces. But the shohin will probably go in also. Maybe I’ll split the two big tridents up and my 6yr JBPs, some in, some out.

Thanks All

If that space is warm enough for tropicals, then it is too warm for temperate trees to over winter. It needs to be below 40F for most of the winter for proper dormancy

 

[hemmy]

If that space is warm enough for tropicals, then it is too warm for temperate trees to over winter. It needs to be below 40F for most of the winter for proper dormancy

Valid point! I should have clarified that within the garage I was planning on framing 2 temporary, plastic covered grow spaces with vent fans and heat for tropicals and another at 40F lows for live oaks, redwood, etc. The deciduous would have to be outside of those enclosures. I’m not sure how well the garage will hold heat. Since this summer it has been within 10-15F of outside temps. I’m thinking it will be a little warmer in the winter. But I’m guessing it might freeze if temps stay below 0-10F for any prolonged period.

Luckily, I have some time to prepare since it isn’t supposed to get below 40F or frost, until this Friday and Saturday (oh, crap!).

 

[Paradox]

Valid point! I should have clarified that within the garage I was planning on framing 2 temporary, plastic covered grow spaces with vent fans and heat for tropicals and another at 40F lows for live oaks, redwood, etc. The deciduous would have to be outside of those enclosures. I’m not sure how well the garage will hold heat. Since this summer it has been within 10-15F of outside temps. I’m thinking it will be a little warmer in the winter. But I’m guessing it might freeze if temps stay below 0-10F for any prolonged period.

Luckily, I have some time to prepare since it isn’t supposed to get below 40F or frost, until this Friday and Saturday (oh, crap!).

When I kept things in the garage here in zone 7, it often was too warm in there and I had problems with things leafing out too soon in the spring. It was very difficult getting things acclimated to outside and the 2 step was a thing. I had some trees die because while it was warm enough, the wind would shrivel new leaves. So I would be very careful of the garage.

Since I started using a cold frame for my deciduous, I havent had those problems.

Also do you have a basement? I have my tropicals in my basement during the winter under lights that keep them warm during the day.
I dont need to provide supplimental heat for them down there and they do just fine. It would save yourself building spaces in the garage and also save the electricity from heating and venting....lol

Think simple. The more complicated you make it, the more expensive it could be and could cause issues.
A friend of mine has an unattached garage he put his trees in with a heater to keep it above 30 degrees.
The heater had a malfunction and blasted the garage with heat for a couple of weeks before he noticed.
He lost a good number of trees along with a big maple that was a pretty penny for him.
He is switching his trees over to a cold frame now.

 

[hemmy]

I had some trees die because while it was warm enough, the wind would shrivel new leaves. So I would be very careful of the garage

Good to know. I hadn’t thought about the tenderness of new leaves. I will rely on the block coldframe for as many trees as possible. I will also move it to a better shaded spot under the pergola against the house. Where it won’t get the morning and noon sun of the other spot.

Should I keep the pines and junipers in a spot that gets some morning sun vs the all day shade?

I’m guessing tropicals will have to go to deep shade to re-acclimate in the Spring. My ficus also have thick cuticles. But I seen sunburn on leaves from hard cutbacks exposing more interior growth.

 

[ShadyStump]

Most common tropicals won't handle the winters in KS. Some will go dormant and lose their leaves in winter, but won't take a hard freeze. Some gardeners around here can keep peppers alive in the ground over winter by mulching them heavily, but they usually come back from the roots or the lower trunk. The branches are lost.
I just bring my tropicals inside. They sit in the big living room window with supplemental lighting.

 

[Dav4]

Good to know. I hadn’t thought about the tenderness of new leaves. I will rely on the block coldframe for as many trees as possible. I will also move it to a better shaded spot under the pergola against the house. Where it won’t get the morning and noon sun of the other spot.

Should I keep the pines and junipers in a spot that gets some morning sun vs the all day shade?

I’m guessing tropicals will have to go to deep shade to re-acclimate in the Spring. My ficus also have thick cuticles. But I seen sunburn on leaves from hard cutbacks exposing more interior growth.

I always recommend an overwintering spot out of the sun and wind. A steady wind when daytime temps are in the low 20's (so frozen root ball) and dew points in the single digits is a recipe for freeze drying foliage.

 

[Deep Sea Diver]

Some great advice here!

One major issue about wintering over dormant trees in freezing temperatures is in direct sunlight the trunk/branch cells can dissicate because frozen roots are unable to replace the water lost through evaporation in these cells.

(Who would’ve thought trunk/branch cells could evaporate water.)

Worst case scenarios are sun scalding (literally blistering) and trunk splitting (frequently not recoverabl). Most trees from pines through azaleas can be affected.

cheers
DSD sends

 

[Paradox]

I keep all my temperate trees in my coldframe which is on the north side of my house. There is a 6ft tall fence on the east and the west sides of it.

The trees get very little if any sun. It's protected from wind and I can cover it if temperatures drop too far below freezing for my liking.

The temperature fluctuations in the springs be greater if I put them in another spot and could cause problems.

 

[hemmy]

So I built a quick test cold frame up against the house from blocks, 3' W x 6' L x 4' H, covered with boards and thick blankets to protect some trees from ~28F since we hadn't been below 40F yet. It worked well and the temp inside stayed at 47F. But since the next 2 nights were sub-20s, I brought everything into the garage at 51F. The cold frame floor is partially over a concrete patio slab against but not connected to the house slab. The rest of the floor is paver stones with gravel/sand (the last guy's DIY project). I put a thermostat over a foam pad on the concrete and under blankets and then covered the cold frame. We hit 21F and 19F the last 2 nights and the temp inside the frame stayed at 51F.

I'm more comfortable with the idea of using a cold frame now. But I still have some questions. This winter as we have temps stay below freezing for longer periods the floor of the cold frame will lose heat to the surrounding colder soil and slab. Which will lose heat faster, the slab or the soil?

I assume the slab, but if it is dry I wouldn't think it would conduct heat very fast. I plan to lay down a sand/gravel base for better drainage and the proper cold frame will be lined on the inside with sheet foam insulation, with insulated lid. Would you do something different for the floor?

I understand the goal of letting them stay frozen and just mulch them in for the winter. But the reality of my local climate is that there will be numerous freeze/thaw cycles throughout the winter. Our frostline is 30", but even 2" & 4" average min. historical data for winter shows ranges from 25F - 55F across multiple winters. I'm hoping the cold frame uncovered/covered moderates the temperature and keeps them in a 30F-50F all winter. The downside is that will have to water more.

Hardy trees are all going back out today, since the long range is for nights in the 30-50F range. I hope they'll get able to get the gradually colder temps needed for dormancy before we get nights back in the 20s. I'm thinking by time it reaches those consistent temperatures, the trees can be mulched in the cold frame but uncovered.

What temps do you cover or close your cold frames?

Thanks for all the help!

 

[ShadyStump]

The slab will lose heat faster than the ground, but not so much that you need to worry about it.
50F is as high as you want it to ever get in there, between 30 and 40 all winter is ideal for avoiding damage altogether, under 20 is where you might think about worrying for their first real winter. Anything that pulls through come spring will be fine next winter with just mulch and a windbreak.

 

[HENDO]

Anything that pulls through come spring will be fine next winter with just mulch and a windbreak.

I'm really enjoying this discussion, especially seeing real world temperature range examples given out.

@ShadyStump can you elaborate on the above? Does this mean for some reason if plants survived in the current setup this Winter, they would only need the mulch/windbreak next Winter?

 

[ShadyStump]

I'm really enjoying this discussion, especially seeing real world temperature range examples given out.

@ShadyStump can you elaborate on the above? Does this mean for some reason if plants survived in the current setup this Winter, they would only need the mulch/windbreak next Winter?

Keep in mind that I'm giving what little help I know because I have firsthand experience in the climate he's in.

OP's trees are coming from mild southern California winters to the Midwest plains where winters are full of swinging extremes; almost as extreme as my climate. There's some concern as to how his trees will handle their first winter in the new location.
The comment in question is specific to that. I figured if his trees do alright this first winter, they'll be mostly acclimated so that next winter won't require near the level of protection. They're all technically hardy to his climate, but this is the first time they've actually experienced it.

 

[Paradox]

What temps do you cover or close your cold frames?

I cover my cold frame when temperatures are forecast to be below 30 for a significant amount of time (days) or if it's going to be below 25 overnight

 

[Deep Sea Diver]

So I built a quick test cold frame up against the house from blocks, 3' W x 6' L x 4' H, covered with boards and thick blankets to protect some trees from ~28F since we hadn't been below 40F yet. It worked well and the temp inside stayed at 47F. But since the next 2 nights were sub-20s, I brought everything into the garage at 51F. The cold frame floor is partially over a concrete patio slab against but not connected to the house slab. The rest of the floor is paver stones with gravel/sand (the last guy's DIY project). I put a thermostat over a foam pad on the concrete and under blankets and then covered the cold frame. We hit 21F and 19F the last 2 nights and the temp inside the frame stayed at 51F.

Not sure you will need the heat pad, yet good to have.

I'm more comfortable with the idea of using a cold frame now. But I still have some questions. This winter as we have temps stay below freezing for longer periods the floor of the cold frame will lose heat to the surrounding colder soil and slab. Which will lose heat faster, the slab or the soil?

Concur with @ShadyStump the slap will cool a bit faster, but not appreciabl.

I assume the slab, but if it is dry I wouldn't think it would conduct heat very fast. I plan to lay down a sand/gravel base for better drainage and the proper cold frame will be lined on the inside with sheet foam insulation, with insulated lid. Would you do something different for the floor?

Side insulation won’t hurt and likely will help. Only reason to have foam would be to put under the heat mats.

One of the key planning items for cold frames and greenhouse is drainage. This is the very first consideration after selecting a location. Have you evaluated/tested this factor yet?

I understand the goal of letting them stay frozen and just mulch them in for the winter. But the reality of my local climate is that there will be numerous freeze/thaw cycles throughout the winter. Our frostline is 30", but even 2" & 4" average min. historical data for winter shows ranges from 25F - 55F across multiple winters. I'm hoping the cold frame uncovered/covered moderates the temperature and keeps them in a 30F-50F all winter. The downside is that will have to water more.

If you have a frost line of 2-4” likely the trees will stay dormant. Thats the key, staying dormant, not freezing. (Chilling hours are not accumulated below 32F/0C.).
The ’cold box’ will moderate temperatures only if closed. (btw: Dormant trees do not need sunlight.)

Hardy trees are all going back out today, since the long range is for nights in the 30-50F range. I hope they'll get able to get the gradually colder temps needed for dormancy before we get nights back in the 20s. I'm thinking by time it reaches those consistent temperatures, the trees can be mulched in the cold frame but uncovered.

What temps do you cover or close your cold frames?

Only when freezing weather is predicted, (close in the evening, open about 35F.

Thanks for all the help!

Well done!
Good luck!
DSD sends

 

[hemmy]

Not sure you will need the heat pad, yet good to have.

"I put a thermostat over a foam pad on the concrete and under blankets and then covered the cold frame."

That was a typo, for this test cold frame it was my remote temp sensor sitting an old "yoga" mat. No heat was added. I had planned soil cables, but from one feedback the heating mats were more effective. I need 2 cold frames and the other spot doesn't have a working exterior outlet.

One of the key planning items for cold frames and greenhouse is drainage. This is the very first consideration after selecting a location. Have you evaluated/tested this factor yet?

One location is where I had a bonsai bench and it drained well and away from the house. But the 2nd location is also against the house, but in an area where drainage is tricky. They convened the downspot further away to avoid a low spot. That spot has the "L" shape of the house and I could see snow piling up from the off the roof. I'll have to put down some gravel and bring it up a few inches to make sure it drains well. That's helpful, thanks you.

 

[hemmy]

On the second cold frame, I'd like to put in my pines with escape branches in without having to lay them over when I want to close it up. But that requires 5' height clearance. I was thinking of making that one as a large wooden box with a fold up lid and fold down segment on the length. Also using foam insulation inside. Any reasons not to do that or do it differently?

Thanks!

 

[Deep Sea Diver]

A pop up and pull down? Seems reasonable on the surface.

As you recall conifers photosynthesize all winter and have much less sugar storage then deciduous trees. So the more light the better. Not saying it won’t keep the trees alive shut all winter, but they likely will be quite a bit peaked by spring time.

btw prepared for critters in each space?

cheers
DSD sends

 

[ShadyStump]

A bit of rat bate in each will be plenty for rodent control.

If the one for conifers has a pop-up lid, that can be opened during the day when the temps are reasonable. That will go a long way.