Safe for Tomatoes in unheated greenhouse?

Community Community General Gardening Vegetables Safe for Tomatoes in unheated greenhouse?

This topic contains 6 replies, has 5 voices, and was last updated by  Spring 8 years, 8 months ago.

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    Is it safe to plant out Tomato plants in the border of an unheated greenhouse (25th April)?

    I’ve read that low temperatures can destroy cells in the forming flower buds and lead to misshapen or catfaced fruit.




     Darren, in view of the forecast cold nights, for at least the coming week, with a risk of frost which may or may not reach leaves in unheated greenhouses and tunnels, I would hang on as long as you can, 

    Your comment seems more about low temperatures rather than frost. I have often grown tomatoes in night temperatures of, say, 4-8C and the fruit have been fine. Freezing is the main concern but do keep us posted.


    Alan McAteer

    Do you have a max-min thermometer in your greenhouse? I would suggest you use one as a guide, tomatoes do not like temperatures much below 10 degC in the evening. Also check the soil temperature in your greenhouse beds…ideally this should around 10-12 degC. If you can keep your young plants in good light and warm then I would wait until mid- May before planting out. Some growers I know would not plant out until the first flower truss had appeared…they reckoned that by waiting until the first truss had formed the plant then puts most of it’s energy into fruit production rather than vegetative growth. May I suggest you do a few trials and perhaps plant out some( same variety) plants now, hold some back and plant later and see what happens. I am planting some of my plants in straw bales this year for the first time in the hope that the extra warmth from the straw may help somewhat!

    I,like Charles, have had a good crop in spite of low evening temperatures but if you are only growing a few plants then I would try to maximise your yield by holding on until evening temperatures stabilise. Also don’t forget that light levels are often more important than temperature.




    I was just about to ask the same question about unheated polytunnels. Although I have an additional problem in that I have quite a few leggy tomato plants that really need the extra light… Is it work the risk planting them in the poytunnel now? or should I throw them away (I’ve got some new seedlings just coming up. Yes, I planted too early… it’s my first year growing tomatoes I didn’t realise how fast they could grow!



    Hi Spring
    you can still plant your tomatoes. Lay them along the soil and cover the stems with compost. the stems will root and the tips will grow up (don’t cover all the legnth of the stem). You will also get a bonus of stems growing out of the leaf axils.



     Good tip from Peat and also the weather outlook is improving now, plants can go out if you have fleece to lay over them at night in case of a final stray frost.



    Thank you both I shall do that today. (and pot up the seedlings I planted a week ago in case of failure!)
    Have a lovely sunny sunday!

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