Hi bosewichte,

Well, of course, it's hard to tell what may have caused your problems by just reading your post. Basically, it sounds like you did everything about right. There are a few things that I do wonder about however; they may or may not be the cause of the problems.

First of all, I think you should get a thermostat for your heat mat. Without it, you really don't know what the temperature of the growing media is. Usually, you don't want the temperature to go over about 75 or 76 degrees.

Then, you mentioned filling and using plastic dixie cups. Actually, they're pretty deep for seed germination. To prevent the growing media from staying too wet, shallower containers probably would have been better. In any case, you want the media to be moist and not wet. When the seeds germinate, their roots will need oxygen, which can be driven out by too much water.

Also, watering seeds from the top can easily cause the seeds to be buried too deep. Most folks agree that gentle bottom watering is the best. If the growing media is moist (not wet) before you put it into the germination containers, and you use the plastic domes, you probably would not need to add any more water until after the seeds have germinated.

My guess is that your seeds ended up too deep and/or the growing media was too wet. You should see slight condensation on the underside of the dome, but if water runs down the sides it's too wet.

Hope this is helpful and good luck in the future with your seed germinating.

Art

You know, my husband was just saying today that I should've bought a thermostat. I was trying to save some money. Anyway, I definitely think the heat mat was a bit too hot. And, the water did run down the sides of the dome, so I used too much water. I'm not sure how to bottom water but I'll look it up. About the containers...I've heard of people germinating in yogurt cups so I thought dixie cups would be all right. What would you recommend in the future?

Thank you so much!

bosewichte,

About the containers...You said you bought four large rectangular plastic trays, with domes, for your seeds. If those are the standard 11" by 22" plant trays, you should be able to use the standard 72 cell seed plug trays that fit right inside of those. They're inexpensive and available at most big box stores or hardware stores. If your "plastic dixie cups" are the kind I'm thinking of, they're about three and a half inches deep. The cell plug trays are only about two inches deep.

Art

PS - It's not too late to start again with new seeds, especially with zinnias and cosmos! Zinnia seeds usually germinate in about 3 days and the cosmos won't be far behind. You should surface sow zinnia seeds btw, light is helpful to their germination.

In my experience, if you don't fully wet the 'non soil' soils, you risk having them be wet on top and bone dry throughout. If your mix was already damp prior to dixie cup filling this likely isn't the case.

Andrew

Yes, my trays are that size. I will make a note for next year! I won't replant inside this year, though. I can direct-sow those annuals in a week outside and they'll spring up in no time!

andyinnyc - you are so right. When I dumped out some of the dixie cups to re-use them for new planting, they were wet on top and dry the rest of the way down. Grrrr!

If I had to guess I would say the foam underneath your heat mat may have gotten the planting medium too hot.

I once put some styrofoam under my heat mats, it cooked nearly all my seedligs. You might want to find something to put your heatmat on that will not hold too much heat(I use a wire cooking rack, allows the mat to disperse heat and still warm the medium). Slightly warm is good, hot is generally not.

That makes sense and I have several wire cooking racks. I will be really prepared next year! :)

ballplayer10123, I am surprised to hear that. All mine are on 3/8" styrofoam. They are doing well. I didn't know that it intensified heat. Before I put it under them, all the heat was going into the surfaces I had them on, and the soil was too cool. It's weird how different things are in varying circumstances!

It's fun (and sometimes a real bummer) to see the interesting things that happen in gardening. And after all, none of us use the exact same materials with the exact same conditions, seeds, etc. It's always a gamble! :D

It IS interesting to hear what works and doesn't work for some people. I did feel like in my case, the styrofoam wasn't needed and made my seedlings too hot. I could feel that it was really warm in those domes but I thought the warmer the better for germination! I'm learning so much, though. After doing some research, I went back and re-planted the two things I really wanted to grow, nasturtiums and sweet peas. But, after my research, I decided to turn the heat mat OFF and minimize watering. No dome...just the light on the soil. I've got nearly 100% germination after just 2 weeks!

Next year: thermometer. minimize watering (moist, not wet). plant things that will germinate at the same rate, roughly. know the needs of the seedlings...not all are alike.