It's going to get cold.

[Chris L]

Covering plants with paper is probably like putting a wooly hat on our head.

[SimonT]

I think the idea is that fleece (newspaper or whatever) traps some of the sun's warmth and then slowly cools down overnight.

Last night here we had a -3oC minimum. But it was only -3 for an hour- and most of the rest of the night was just
above freezing. I checked and my small unheated coldframe was still just above freezing when the temperature outside was -3- so at that point it had not yet reached equilibrium with the outside temperature. So given the outside temperature profile, it is quite likely that plants in this coldframe did not experience temperatures below freezing last night at all, even though it is completely unheated and we had a -3oC frost.

I don't use a fleece unless it gets really cold and I also have the coldframe open to some extent for ventilation throughout the winter. If I used a fleece then I would hope it'd just trap a bit more warmth than the frame alone, ready for a really cold night. I stopped watering end Aug and my plants are in dry compost. But in my current coldframe I do sometimes get some condensation which I think comes through the base from wet soil underneath the frame. This mostly runs off the lid but I do get some drips onto the inside. If I put down a fleece the condensation vanishes off the lid and appears on the inside of the fleece instead- ie the plants soon get wet. I think condensation on the plants is more risk than the cold in this situation.

Of course if we get a sustained or severe cold period then even with a fleece plants will experience temps below 0. This is when factors such as how dry the plants are and how frost hardy they are becomes critical!

[Eric Williams]

Hi all, I agree with Akko re the paper idea and fleece, also I think that bubble wrap is ineffective after a few hours and can cause condensation. If only a small collection I move the sensitive ones inside, and my heater cuts in at 3C. This raises my 12x10 ghouse up to 4 or 5 C, then it’s set to cut out. I have a fan running 24/7 and I open door and vents any day the sun shines in Winter. Over the years I have not lost a plant due to cold. If showing these low temps can cause brown marks. Cheers

[habanerocat]

Whenever it gets cold I'm reminded of these informative articles by Philip Greswell.

https://www.jstor.org/action/doBasicSea ... reswell%22

[esp]

Hi all, I agree with Akko re the paper idea and fleece, also I think that bubble wrap is ineffective after a few hours and can cause condensation. If only a small collection I move the sensitive ones inside, and my heater cuts in at 3C. This raises my 12x10 ghouse up to 4 or 5 C, then it’s set to cut out. I have a fan running 24/7 and I open door and vents any day the sun shines in Winter. Over the years I have not lost a plant due to cold. If showing these low temps can cause brown marks. Cheers

I'd assume that bubble wrap is useful for heated greenhouses and also effective if there is significant daytime warming from direct sunshine but more-or-less useless for prolonged daytime cold temperatures when there isn't any heat available to keep in.

[SimonT]

Some sort of thermostatically controlled electric heating would seem to offer the best protection against cold in most cases. Even if it is just heated to provide frost protection. Some people might want more insulation (giving more condensation) but saving on heating costs, or others a more open growing environment, which might have less condensation but might be more expensive to heat.

But the original thread was really about the use of fleece/newspaper as insulation? If the space is heated then I can't see this making much difference, even if the thermostat is under the fleece. But if it is not heated then these layers might "hold" a few extra degrees for a few hours, depending upon exactly how it was used? I would argue that in short cold-snaps this could make a difference- but not in prolonged periods of cold.

[TomInTucson]

At our southern border, we have had record numbers of undocumented immigrants seeking asylum (& expatriation). They are often given these to stay warm while waiting to be assimilated by our ICE (Immigration and Customs Enforcement): agency



I wonder if they would work for temporary coldest evening plant protection?

[Paul in Essex]

Small children? Probably. Might go through 2 or 3 on the coldest nights.

[el48tel]

Nice idea
But
These 'space blankets' work by reflecting heat back. You stay warm because any residual warmth in your body is reflected back towards your body rather than lost into the surroundings.
Our plants are hardly warm radiating bodies therefore would not really gain. The fleece idea is probably the best because the fleece traps the air movement and stops the turbulent air flow which causes the most rapid cooling effects. The 'space blankets' could become a cold surface on which condensation would form which would not be beneficial for our plants.

[TomInTucson]

The last few nights (and days) have been almost 20°F below the norm here. This current condition has been the impetus behind a few TV news stories with interviews from several local cactus nurseries showing a variety of methods that are used to avoid cold damage to their inventory. The most popular method is to place a Styrofoam drinking cup over the growing tips of the narrow cereoid cacti. Another method is the use of what is called frost cloth for shrubs, and ground cover bedding plants. The advice on the proper use of this cloth is to make sure that a number of stakes be inserted around the vegetation needing protection before placing the cloth over them. The theory behind its efficacy is; since the ground is almost always warmer than the air on cold nights, the warmer temperature can be trapped underneath the cloth. The reason behind the use of stakes is to keep the vegetation away from the cold air.

I can't verify the use of either technique, since I bring ,indoors my most sensitive plants (potted), and I only plant in the ground what I believe are species (and hybrids) that are either native here, or are from climates similar to mine.

The reason I posted this image:



was to possibly use it in a similar method advised for the frost cloth.