Slowed by the cold. That's if they don't rot from sloppy wet soil from sitting so long in water. So be sure to let the soil drain out the excess water as quickly as possible. If you are using a plastic cover then prop it open so some of the humidity can evaporate out.

Dave

I'm a newbie (so take my info fwiw), but I soaked my tomato seeds for a couple of days before sowing and they did not rot.

They will just delay germination. Cold does not harm un sprouted seed.

sey

> I'm a newbie (so take my info fwiw), but I soaked my tomato seeds for a couple of days before sowing and they did not rot.

it's a long time considering tomatoes already sprout rather quickly.. might not rot, but it can water log the embryo. from my experience, they might even sprout, but growth can be stunted.
tomato seeds have a thin fuzzy hull that softens pretty easy by just being sowed in damp soil, so if you must, i don't recommend soaking them more than a few hours.. some other seeds such as beets, 24 hours would be fine.

I germinate my seeds on wet paper towel. Being very wet has actually made them germinate faster. I haven't had problems with seeds rotting.

The issue when talking about a relatively short 24 hour time frame is more the cold than the wet. Cold + wet can lead to rot, but I don't think 24 hours will cause problems if you're using soilless mix. If you used garden soil or a mix that is labeled "soil", then there could be organisms in it that could rot the seeds in cold, damp conditions.

Thank you everyone for your responses! My outlook on the success of this flat of tomatoes is much improved.

Steve- that's interesting about soaking the seeds too long. They all sprouted 3 days after planting, but I have no idea if they are stunted, as I have nothing to compare them to. I'll have to do it diffferently next year and compare results.

There's no reason why they would be stunted. If they sprouted within 3 days, they're clearly viable, happy seeds.

I just came to this forum with a similar concern. I start all my seeds in an unheated mudroom, which is kept very warm and humid from the grow lights. 5 days after I sowed my tomato seeds, my sister's boyfriend accidentally left the outside door open for about 5 hours at night, when the grow lights are off and the outside air temperature is around 5C. It's now been 8 days and they haven't germinated. My main concern is that their growth, if they do germinate, will be stunted.

What is the basis for assuming cold experienced before germination will stunt tomato growth?

Well, I was thinking that 5 days after sowing, they probably had started to germinate. I always thought that any form of stress in the seedling stage can permanently stunt plant growth, but I could be wrong. From a quick look at the literature it seems like exposing tomato seedlings to temporary cold stress doesn't effect yield, which is surprising to me.

Delayed germination isn't necessarily related to how the plant will grow.

And exposure to cold as a seed is very different from frost damage on a seedling.

Volunteer tomato plants emerge all the time in gardens all over the world from seed that overwintered from the previous fall, and volunteer plants often become big, vigorous, and productive.