I tried to germinate lettuce indoors at 27 degrees Celcius (80 degrees Fahrenheit) in the day and 17 degrees Celsius (62 degrees Fahrenheit) at night, but they did not germinate. What is the most favourable day and night temperature for Grand Rapids lettuce seeds germination?.

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    Since lettuce is photodormant, it will not germinate in the dark. Place your tray under fluorescent lighting within an inch of the bulb or in a south facing window where the seeds get sunlight at least 3-4 hours a day. Your temps sound good.
    – Brenn
    Oct 31, 2016 at 18:54
  • For real Brenn? I am going to bug you for more info on this photodormant...whoa..
    – stormy
    Nov 1, 2016 at 5:41
  • Brenn...make this an answer and please more information, please?
    – stormy
    Nov 1, 2016 at 5:42
  • @Brenn I've just read a few things indicating that the temperature range is fine. I haven't grown it or know anything else about how, so I'm with stormy. If you have time to make this an answer it would be interesting. Thanks! Nov 1, 2016 at 21:30
  • I thought it was relatively known that lactuca seeds need light to germinate. @stormy, knowing you want to know more about photodormancy, take this one. Lots of info on the net about it.
    – Brenn
    Nov 2, 2016 at 1:12

1 Answer 1


It does sound quite hot for lettuce germination. For those of us in the US, that works out to 62F at night, 81F during the day. Grand Rapids is an heirloom variety from here where I live in the Great Lakes region, where lettuce is grown in the spring and fall. That means temperatures generally hover in the 40's at night (around 4-8C) and only get into the 60's during the day (17C). Given that the climate you are trying to grow in is very different, you might do better with a different variety.

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