Is my poly warm enough?

[Plot No.69]

Hi all.  My unheated Polytunnel is a good 10-15 degrees warmer than outside temp during the day.  Is it likely to retain sufficient heat at night to safely put toms and cues in?   Also, has anyone put courgettes out into ground yet?  I can barely see out of my home windows for all the plants on window cills. Any help much appreciated! 

[Plot No.69]

[steveg1966]

What I would is get a minimum/maximum temperature thermometer and you will be quite supprised with the extremes in the air temperature in your polytunnel over the last week mine as got as high as 115 f(46c) and as low as 29.3 f (-1.5C) at night so the air temperature will not stay but the ground temperature will be much higher than outside.My plants have been fine for 2/3 weeks in my tunnel but most of these the hardy ones such as cabbages broccoli etc and they are fine I think its too early for tomatoes cucumbers  and other non hardy ones especially with such a cold slow start to spring.

[chriscross1966]

Max-min thermometers are a godsend, I've got two in the GH and another one outside.... I reckon mine is 10+ degrees warmer in the day and about 4 warmer at night, but wheras the outside temp can go down quite fast and stay there for several hours, the GH slowly sinks and then rebounds as soon as the sun comes up...a poly isn't quite as buffering but a cold-frame in a poly would be....

[Digeroo]

Have you tried putting a tub of water near them, it heats up during the day and is slower to cool at night than air.

[Jayb]

Might depend on what part of the country you are. I've had tomato plants in an unheated poly-tunnel for the last week-ten days. They look to be doing well and I hope to plant the larger ones in the border in about a week or so. I've fleece standing by if it gets too cold. I've only just sown my courgettes and cucumbers though.

[galina]

Have you tried putting a tub of water near them, it heats up during the day and is slower to cool at night than air.

There is a variation on this - brown water.  For example ready diluted comfrey liquid in milk bottles laid flat on the ground next to each plant.  Darker liquid gets warmer during the day than just water and the ready diluted comfrey liquid will soon come in handy as fertiliser for the tomatoes.  The bottles flat on the ground between plants also prevent the ground cooling overnight.


There is a product called Wall o' Water but only occasionally available in the UK.  This is a good frost protector for tomato plants outdoors or in greenhouse/poly.  It looks like this:
Picture found on Google:
http://www.judydailey.com/wp-content/uploads/wall-o-water.gif

There is a homemade version of this very effective frost protection method and I apologise that it comes from a different forum:
http://www.growfruitandveg.co.uk/grapevine/vegging-out/homemade-wall-o-water_55545.html

[brown thumb]

Thank you Galina that was an interesting bit of info ,I   see they mentioned a green house made out of plastic bottles ,my gransons school did this a couple of years back  have any one got any building info on making one of these ,as i would like to have a go .  I  Work in a canteen so plastic bottles is no problem to source

[GREGME]

Hi if it really is 10-15 celsius warmer inside it is easily warm enough and zero frost risk. I'd go for it.

[Plot No.69]

Thanks all. Think I'll experiment with two plants (I have 15 others romping away at home). I'll report back on their condition.

[manicscousers]

Our toms have been in for a couple of weeks, I just keep some fleece handy 

[galina]

I   see they mentioned a green house made out of plastic bottles ,my gransons school did this a couple of years back  have any one got any building info on making one of these ,as i would like to have a go .  I  Work in a canteen so plastic bottles is no problem to source

Brownthumb, here is one

http://www.nead.org.uk/downloads/pdf/bottle_greenhouse.pdf

[brown thumb]

Thanks for the info ,great set of plans and shopping list as well