Insulating your greenhouse with bubblewrap

LynfromSea

Wondering whether I need to do this as it sounds quite an effort.
I have rose cuttings, pelargoniums, Salvias (greggerii) and I’m propagating some cornflowers, sweet peas and Centurea. I’d be very grateful for any any help on this.

nutcutlet

I think only the Pelargoniums would need extra protection so maybe a bit of fleece for them or a windowsill indoors

Joyce Goldenlily

Lining a greenhouse definitely helps to keep the temperature above freezing.
I am going to have to cut my bubble wrap into narrower strips to thread over the canes I have put along the inside of the ridge of my greenhouse. As you say, it is a fiddle but when there is 6ft of snow outside and the temperature is plummeting, it will be worth it. I am not planning to heat my greenhouse as I do not keep any very tender plants that need overwintering, in it, they are in the conservatory.
It is also a faff to take the bubble wrap down so it depends on how committed you are to keeping your plants going during the winter. A lot of plants depend on minimum light levels rather than minimum/maximum temperatures. The winter light levels in this country are not enough for a lot of plants to be happy and survive.

Kili

Pelargoniums wrapped up too tightly will suffer from mildew unless you ventilate well. I had a batch of a 100 Pelargoniums in my greenhouse over winter a few years ago and 75 of them succumbed to mildew. It was too cold to ventilate and too humid for them to survive. Find the right balance and they will manage. I had to take the remaining 25 in to the house where they all did well until late spring when they were planted out.

Butterfly66

I overwinter pelargoniums in an unheated greenhouse. I group all the pots together and just loosely lay a fleece over the top

Allotment Boy

Yes following on from @Joyce Goldenlily remember that  bubble wrap will further reduce the light levels,  so like everything it's  a trade off. I  used to do it  but don't anymore, I  keep a few really tender things in a double height propagator.  The challenge then becomes when you need to sow your seeds. 

Lyn

I used to use it,  and leave it on all summer for sun protection,  it didn’t last long,  went to dust after a few years. Bits of plastic everywhere. 

 I don’t use or need it now,  what I overwinter doesn’t require anything other than frost protection,  the main thing is keeping the pots fairly dry,  especially pelargoniums or they will rot. 

If it’s especially cold I put the pots under the bench for extra protection. 

thevictorian

I think it depends on how good your greenhouse is. If it's well constructed and not full of holes, then some emergency fleece might work better on the colder nights.

LynfromSea

Thank you so much all of you as you have come up with some great suggestions.
I think I will being the Pelargoniums into the house and put a fleece over the rest when frosts are predicted. Having said that I can’t always rely on the weatherman as he’s often wrong as here in the South West we sent to get more than our fair share.
it sounds so obvious to just cover them with fleece but it never crossed my mind so BIG thanks to you all.

Nanny Beach

I bet when you say unheated green house,you really mean frost free. I have too many pelargoniums to keep indoors. The bubble wrap stays on quite a few years at a time. When frost is predicated,an extra layer goes over the citrus. That green house also overwinters fuchsias, begonias. If it gets really cold,there is a little tubular electric proper green house heater. On sunny winter days the door will be open for a few hours.(obviously after turning off the heater,we have economy 7)

Fairygirl

As @Nanny Beach mentions @LynfromSea - there's a fair difference between a cold greenhouse, and a frost free one, although most people probably feel it's the same thing. It comes down to what's going in them though. Some plants only need basic protection from poor weather, whereas others need warmth to survive at all. Wet cold does far more harm than dry cold too. 
I'd agree with @nutcutlet- the ones which need protection most are the pelargoniums. They won't take much frost for any length of time. I can't comment on the salvias as most of them require help here to get through winter. The others are all bone hardy. Sweet peas, for instance, only need some basic shelter from the roughest weather, or they become leggy and weak. Against a house wall is often enough, or cold frame with the lid opened a bit. I'd reckon the cornflowers and centaurea would be the same. I've never kept them in a g'house