How hot is too hot for seed germination?

[Runningwater]

Orginally posted this in the Pepper forum and then thought it might get a better chance of an answer over here. I was going to try germinating my pepper seeds this year before transplanting into starter cups with granular DE for a seedling medium. So I had pepper seeds in damp paper towels in a tupperware on seed heat mat, put a dish rag on top and didn't check them until about 24 hours later and it was much warmer than I expected. I'm guessing around 110 degrees? Have I killed the seeds and need to start over - or will they be OK?

Any advice welcome - want to restart ASAP if that's the answer - thanks!

[Stvrob]

When my thermostat malfunctioned once the heating mat got up to 112 degrees as measured by my infrared thermometer. Pepper seed in shallow germination trays didn't germinate, though a few watermelons did.

Was the paper towel still wet when you discovered it too warm? Was the Tupperware lid on? Or was it open to air? Reason I ask, is if it was wet and accessible to the air, the seed temperature probably was kept cooler than you think due to evaporation. On the other hand, if it was bone dry, they are probably toast.

[Ricky Shaw]

Do you have the same confidence in that seed that you had 2 days ago, that's the question I'd ask myself. Because if anything goes wrong with those plants, I'd have doubts about my decision. That in itself is enough to make me start fresh seeds.

[TomNJ]

I typically start my pepper seeds with a soil temperature (top 1/4") in the mid 90s for the first few days, then drop it to the mid 80s. I have exceeded 100°F before without issues. Since you are only talking about 24 hours, I agree if they were wet they should be okay. In fact they may sprout faster.

TomNJVA

[Merediana]

The pepper forum I'm part of suggest never going above 86°F for best results and some say that their germination has been badly affected at around 95°F (soil temperature!).

[loulac]

Several publications deal with that subject, I remember picking up the following information :


Tomatoes - lowest temp : 10 C 50 F best range : 16 C 61 F / 29 C 84 F best temp : 29 C 84 F Maximum : 35 C 95 F
http://www.heirloomseeds.com/germination.html gives slightly different figures
optimum soil temperature : 24 C 75 F to 25.5 C 78 F

[greenhart]

I lost control of the temperature in my seed starting chamber and let it spike to 100 degrees. I have only a few tomatoes to come up I'll start over again with a closer watch over everything. There is a name for this, it's called 'life'.

[loulac]

Originally Posted by Runningwater

...going to try germinating my pepper seeds this year...

I read your post too fast and did not notice you were asking questions about peppers. I'll try to correct my mistake and suggest some information :

http://www.heirloomseeds.com/germination.html
Pepper : optimum soil temperature for germination days to germinate at optimum soil temperature
25.5 to 29.5 C 78 F to 85 F 10 to 14 days


You’ll find more info here :

http://www.tomatoville.com/showthread.php?t=8154
“Effective germination of tomatoes, peppers and eggplant - critical parameters”

I’ve picked up several key sentences :
I have found that pepper seeds prefer a warmer soil than tomatoes for germination. Even so, many peppers take much longer to germinate than most tomatoes. I have had peppers take 2-3 weeks under less than ideal temperatures. I often soak peppers in +/- 80° water while prepping their trays...it seems to slice a few days off of the germination time.
With hot peppers, a chicken egg incubator set at 80 to 85 degrees works better. Tomatoes generally do best at 70 to 75 degrees.

[lavanta]

I find this very useful, I don't remember where I got it from.

Cheers
Levent



[Runningwater]

I hedged my bet and replanted, but kept the others to see what will happen. If they are OK I'll be supplying the neighborhood with various peppers! I'll let everyone know if they sprout!