A peek under the covers.

[EdMcKenna]

I had been wondering what the consensus was regarding fleece covered cacti in cold greenhouses, namely to peek or not to peek?.
I have tended to leave mine covered given the struggle to separate fleece from spines combined with only being able to see during daylight at weekends due to work times.
Today I peeked and seen the latest blow the winter has dealt to my collection.
Moulds seems to be rampant, but I split the damage into two portions, one tray which was doomed and one which might be saved.
I have cut mushy parts from:
30 year old Parodia lenninghausii,
Stenocereus thurberei,
Austrocylindropuntia,
Echinopsis subdenudata,
Mamm decipiens var campotricha which was wet at the roots possibly due to coir in the mix.
I try to ventilate as much as I can but it's not always an easy call when it's minus 3 or raining when I go to work and then find it rises to above 5 degrees for a few hours during the day.
I have attached pics for reference, I hope I won't sustain much more damage this winter as I have already lost a few old specimens

[edds]

Sorry to see that Ed. Been a funny old winter, that's for sure.

[EdMcKenna]

Thanks, it seems to be a dire combination of extended cold and damp
Roll on Spring.

[juster]

Bad luck Ed, it's certainly been a difficult winter, with extreme cold and damp. Hope your rescue operation works.

[Cidermanrolls]

I’ve detected a large amount of misunderstanding about frost protection on social media this winter.
Fleece covering of plants will protect them from ‘ground frost’ but it will not insulate plants from long periods of ‘air frost’. The internet is full of better explanations of the difference than I could give here.
In most UK winters we have overnight sub zero followed by daytime thaw. This year we’ve had constant sub zero. This year fleece probably has given little protection.
Indeed, if used for long periods fleece or bubble wrap could actually make matters worse for cacti as it risks creating a localised area of increased humidity as the living plant breathes.
I’m lucky enough to have electricity to my greenhouses and, even though the thermostats are set at just a couple of degrees above freezing, I’ve lost no plants to frost. The few cacti I have outdoors, under cover but open to the elements, have also all survived, it appears.

[Chris L]

Reminds me of the winter of 2010/11 (or 09/10) [both were bad, and far worse than we've had so far this year].

A non-thaw the following day is worse than low night temperatures.

Fleece and/or paper stops the freeze falling on the plants but won't keep them warmer if there is no additional heat.... loft insulation does nothing to keep the heat in a house if there is no central heating on for instance.

edited for tpyo.

[SimonT]

I think the idea is that the fleece warms up in the winter sun and retains some of this heat.
Outside it also physically keeps frost and snow off the leaves and the growth tips.
Of course this protection only goes so far.

[edds]

I think the idea is that the fleece warms up in the winter sun and retains some of this heat.

This idea has always intrigued me (and I've heard it a fair few times). If this is the idea then why not make the fleece black so it heats up more quickly, rather than white?

[el48tel]

I think the idea is that the fleece warms up in the winter sun and retains some of this heat.

This idea has always intrigued me (and I've heard it a fair few times). If this is the idea then why not make the fleece black so it heats up more quickly, rather than white?

Black cools faster than white

[Paul D]

I thought the idea was to trap airspace which acts as an insulating layer, cooling down more slowly after warming in sunlight, rather than the fleece itself insulating. The same principle as wearing lots of layers when winter hillwalking (or summer, up here)