Cold protection in greenhouse

[mrsbusy]

Just wondering if fleece covers over tom's aubergines and peppers in a cold greenhouse is enough to protect against night time temperature. I have plants indoors in South facing windows starting to look a bit leggy. Bit of a faff to bring the plants in every night. Your opinion please. I'm in South Oxfordshire - last frost.usually second week May. Last year late frost damaged tomatoes in cold green house so don't want a repeat - I had covered them with newspaper to no avail! Or does it have to be a small heater? Could use an old fan heater...

[Penellype]

Its far from ideal to move plants from a warm windowsill into an unheated greenhouse just as the weather is about to turn cold. Obviously this has to be weighed up against any likely damage caused by keeping them indoors for another week in terms of leggy plants and potentially breaking them when moving them.

I think it is likely that the temperature will drop to freezing or possibly just below in most areas at some point next week. Greenhouses do not hold heat for very long but how cold they get will depend on how much sunshine they have had during the day. Clear skies are a double edged sword as they produce plenty of daytime warmth but also the coldest nights. I think it is unlikely that skies will be very clear, but this also means that the greenhouse will not start off particularly warm.

When preventing heat loss the best option is plenty of layers. Therefore, if you can arrange some sort of framework around your plants to support it, as many combinations of fleece, bubble wrap, blowaway cover etc as possible will help. You will need to uncover the plants for the daytime so they don't cook, but if you can cover them up just before the sun goes down you can trap some of the heat for a while.

You can also use radiative sources of heat if you have the space - a pile of bricks and/or a black bin full of water in the sun will absorb quite a lot of heat during the day and release it slowly at night. It isn't going to make an enormous difference but might raise the temperature in there by a degree or so. A hotbed made of fresh horse manure would also help if you have the space and can put up with the smell, but that is probably impractical in most situations. A greenhouse heater will obviously do a better job but is expensive to run.

[ameno]

Fleece would likely be enough to protect from frosts, but that isn't the only concern. Tomatoes stall if it gets too cold, even if they are not killed, and will grow very slowly for a couple weeks until they recover. Also, if you forget to remove the fleece one morning and it's a sunny day your plants could end up baking.

Personally, I would just leave them on the window and let them get leggy. My tomatoes are already very leggy, but I'm not really concerned. It's an easy problem to fix with tomatoes, as you can just plant them deeper when you come to planting them out.

[mrsbusy]

Fleece would likely be enough to protect from frosts, but that isn't the only concern. Tomatoes stall if it gets too cold, even if they are not killed, and will grow very slowly for a couple weeks until they recover. Also, if you forget to remove the fleece one morning and it's a sunny day your plants could end up baking.

Personally, I would just leave them on the window and let them get leggy. My tomatoes are already very leggy, but I'm not really concerned. It's an easy problem to fix with tomatoes, as you can just plant them deeper when you come to planting them out.

That's ok whilst seedlings but about to pot on and far too many to fit on window sills.
Currently seedlings in greenhouse for the day and loaded onto wheelbarrow to bring in overnight.
Going to put our convector heater in greenhouse - it's got a decent thermostat on it.
Quite agree about planting deep.

[peanut]

I'm also doing the greenhouse shuffle, everything goes outside when greenhouse temps hit 15c and back inside when they drop below.
This year I got some 52cm unheated propagators and they are great for being able to carry 24 x 9cm pots in one go! I try not to pot beyond 9cm until things are ready to go outside full time.

[Jungle Jane]

It does take over your life carrying them in & out every day. I’ve got a few boot trays that carry 21 plants each time,I also pour water in the tray,they have a drink then put the plants in the blowaway,it’s a good system having a couple of trays Some plants could stay on the windowsill permanently till planting time,just give a few days of hardening off,then it wouldn’t be so many to carry. At the moment all my little plants are on trays next to the patio doors & on the windowsills,it’s nice to get them outside in the daytime but my blowaways still in the shed,a job for the weekend

[Bacchus]

I have 54 tomato plants that I'm ferrying between the polytunnel and my house. Only a 20 yard hike, but still a pain. I've increased my Tom's this year as the intention is to sell a few through the honesty box out the front. I've a bit of fleece to use if needed but fingers crossed it 2ont be needed.

[Babru]

My greenhouse has dropped to low single figures overnight, so all my tender plants are staying inside. I don't have 54 tomato plants though Bacchus!

My hardy stuff - sweet peas, nigella, salad etc - was sown in the greenhouse so are all fine.

[annie8]

Haven’t started the in and out to thegreenhouse with my tomatoes yet, but maybe I should next week.

[rary]

If you have electricity in you greenhouse, use a fan overnight, temperature last night was-2c I had some dahlias which I normally cover with fleece, sitting uncovered and they are fine, as moving air prevents frost damage