How cold is too cold for tomato seedlings?

Discussion in 'Gardening & Plant Propagation' started by Tiempo, Mar 22, 2009.

  1. Tiempo

    Tiempo Moderator Staff Member

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    I have 4 flats that started to germinate 2 days ago.

    I'm trying to do them in windowsills, but I don't think it's quite enough light.

    I want to set them outside on nice days and bring them in as necessary, right now they're outside and it's about 50 degrees.

    How cold can they be they safe?
     
  2. postroad

    postroad Well-Known Member

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    I would say that 50 degrees would be the minimum temperature for tomatoes and not for any extended time.

    The sun can make the soil and flats a fair bit warmer than the air temperature though.

    Watch out for the wind which can kill small seedlings at any temperature.
     

  3. MaineFarmMom

    MaineFarmMom Columnist, Feature Writer

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    50* should be fine. My greenhouse is colder than that at night while there isn't any sun to warm the soil. Be careful of wind or strong breeze for a while.

    I visited another farmer in Maine yesterday. He keeps his greenhouses just above freezing at night. His tomatoes are beautiful.
     
  4. Ernie

    Ernie Well-Known Member

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    Any time the plant dips down into the 40's it puts it into a dormant cycle that takes up to 10 days to break. They are a equatorial plant. They like heat. Soil temperature is as important (if not more) as ambient air temperature. I try to stay around 60f if at all possible. I tend to not seed them at all until I can maintain 55+ in my greenhouse.
     
  5. mommagoose_99

    mommagoose_99 Well-Known Member

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    Make a minie cold frame for your tomatoes. Take a large cardboard box and cut the side on a diagnal. Be sure the low side is taller than your plants. If you have a light weight window screen put that over the top of the box to reduce drafts. Any way the purpose of the box is to keep the cool wind off the plants . A covering over the plants will help keep them from being burned by the bright light. Tiny plants need to be hardened off before they spend the whole day outside.
    Your plants are only 2 days old couldn't you use a shop light to give them the light they need. I use 4 foot shop lights sitting on pieces of 4x4's and slide my seed flats under them . I add pieces of 2x4 to raise the lights as my tomatoes or peppers grow.
    Good luck
    Linda
     
  6. MaineFarmMom

    MaineFarmMom Columnist, Feature Writer

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    That hasn't been my experience.
     
  7. Danaus29

    Danaus29 Well-Known Member Supporter

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    I've had mine outdoors during 45*F degree weather and they are still growing like bad weeds. I have to pot them up soon. Lower than 42*F in my experience can cause problems but I've had them come up in my garden and survive frosts and still produce as well as any I've started indoors.
     
  8. Paquebot

    Paquebot Well-Known Member

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    My tomato plants are started 100% outside in a conventional cold frame. The seedlings not only see temperatures in the 40s on many nights but also the upper 30s. The result is sturdy plants much tougher than any that I'd ever seen of those started inside.

    Martin
     
  9. kruizeag

    kruizeag Well-Known Member

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    I don't let mine get under 60 degrees. They seem to thrive best in about a constant 70 degree temp. They do get hardened off before setting in the field. Even then I try to wait until the outside temp is above 50 at night.