hello, I am so sorry to hear about your seeds. I never did impatiens until this year. I had a 72 cell flat that i filled with seed starter mix. So it sounds like pretty much the same startup as yours. Mine started germinating at 5 days.
They look like white stems with hair.Do you know for sure it Is definately mold your seeing and not just the hairy stems?

I did a bunch of research on impatiens online and it said they germinate best at 75f ( That is soil temp not room temp.) Mine was at that temp for 5days while they germinated.So if your flat with the dome becomes too hot that could make them mold. I sure hope this is not to confusing. If all else fails you could germinate them really fast by the baggie method (wet paper towel in a plastic baggie set on top of the fridge or freezer.
I had my flat with the dome covering it and it had water droplets all along the walls.I read that lots of humid air is perfect for germinating, just not good after germination. So humidity is actually really good while germinating. I also put a little digital meat thermometer in a hole in the middle of the dome that let me know the temp of the soil constantly.
Don't give up I am sure it seems hopeless but I am sure there is something that just needs minimal adjusting. Hope this helps :)
I would say you need more humidity, and the dome should stay in place with a soil temp consistant between 70f-75f. I pre moisten the soil with 3 parts soil to a little less than 1 part water then i mix it all up and fill the cells. Then I placed 2 impatiens seeds right on top and then misted them with a water sprayer then I put them in my spare bedroom under two fluorescent tubes for 5 days at 75f soil temp (with dome on top. I kept the light on day and night to keep the temp the same. It worked! I did not really know what to go on except three things lots of humidity,surfaced sown with light, and a soil temp of 75f
I would give that a try, I sure hope it works out for you.

While I'm no expert, I've had great luck germinating
impatiens. That's to say all BUT the double impatiens,
qhich I've not had much luck with at all - the seeds are
much smaller and don't germinate as easily (for me).

What kind of impatien are you trying to grow?

This is the information I got on germinating/growing impatiens...

Seed size varies drastically by color from 35,000 to 90,000 seeds per oz/28 g
Soil temp. must be maintained @ 72- 74F /22 - 24°C at all times. Seed germinates irregularly and slowly @ 60% - 80% in 20 days. Intense direct or artificial light, which is high in the "red" part of the spectrum of light - will limit germination of some colors. We suggest that you start Impatiens on the north side of the greenhouse or shade, flats lightly with blue plastic or cheese cloth. After and during germination, remove plastic or glass, during the heat of the day. Keep medium moist to the touch, but not saturated. Shade seedlings at all times. Never check the plant growth. Using soil that has a neutral pH reading, transplant seedlings at the same depth as they were in the seedling flat - this reduces stem rot at the base of the plant. Grow plants at 60°F/16°C, keep them on the dry side and do not fertilize. Keep transplants well ventilated, and out of cold drafts - which weaken the plants. Allow the plants to cycle through wet/dry periods. Excessive moisture will result in tall, lush growth. Treat with Captan every 10 days to control damping off.

IMPORTANT: New Guinea Impatiens soil temp. must be maintained at 77 - 79°F/25 - 26°C for seed to germinate. New Guinea types should be lightly covered with coarse vermiculite at sowing.

All this being said, I grow mine in my livingroom under
lights - NO heat, just lights. I have a friend who
germinates at 68 degrees and he has excellent luck... We
both use domes - he takes his off right after germination,
I leave mine on a little longer...

Pics:
I found these troths a few years ago - I love them. Not
been able to find them since. (these are germinating begonias not imps):

Partial set up - lights...

germinating imps:

{{gwi:7451}}

After germination:

These are begonias, BUT I treat the impatiens the same -
under domes...
{{gwi:430423}}
Right after transplating:

after transplanting (few weeks later):
{{gwi:7457}}
This looks pathetic, but: (transplanting into bags):

the bags end up looking like this:

I've digressed:

I think hummer above is right with the moisture... I have
lots of condensation - even though I'm growing them at a cooler 65-70 degrees.

I saved seed from last year - if you want some free seed - ?

Thank you Hummer Girl and Tom8olvr! The seeds are Tango, a New Guinea type (I think), though I saw some info suggesting that they are not true NG types. I got them from Parks.

Re-reading my post, I note I left out some info. While the flat was not in direct sunlight, it IS 14" below a single fluorescent bulb which I left on during the day.

Also, I realized later that I had added a small amount of sifted compost into my starter soil (I mix my own from bulk sphagnum moss, sand, vermiculite, and compost). It works great for all my other seeds so I didn't think about the compost.

The seeds are 3 years old, because I haven't ordered from Parks since 2006, and I suspect that may be the real problem. But I keep all my seeds in capped vials that are stored in the refrigerator, so I would think that a few should have germinated.

It definitely IS mold. 0% germination.

The pack instructions said best germination "about 72 degrees", but did not say how many days it should take.

I think I'm going to assume it was their age...

You could always start again! It stinks you went through all the trouble without a single one germinating. If you still feel like trying I bet you could get them to start no problem with new seeds and a flat that keeps humidity in. I thought I would have to be really impatient about the impatiens! But I guess it isn't so.
You could always buy a pack of pelleted tidal wave petunias! They are not for shade, but would give you huge results for the money!
Again, I am sorry they didn't sprout. Keep Gardening, it was probibley you older seeds! :)

I would doubt it's the old seed. I grow older seed all the time without trouble. I mean you might get 85% germination instead of 95% - but you'd still get SOME... I'd bet it's the compost causing the mold. You really need everything sterile. Also I should mention I had a friend that did the mango tango one year and he had horrible germination rates - and hasn't grown them since. It was the first year Burpee came out with them.

Don't let this stop you from doing imps again. They're very versitile and easy once you get the hang of it.

Oh, and lower your lights. I keep might right over the dome...

My professional experience with 'Tango' is that the seed does NOT store well, and old seed = dead seed. We also lightly cover the seed of New Guineas - they seem to germinate better with the extra moisture the covering provides. The seed may also have been old that Park sent you, which may contribute to your problem.

An easy way to acheive the correct temp (without guessing) is to invest in an instant read thermometer for about $7-10. Before you sow your seeds, put the thermometer into the soil of your flat, apply the dome, and put it under your lights. Check the temp after a few hours and adjust the lights up/down as necessary to reach the target temperature range. This works well if you leave the lights on 24/7 while germinating.

On occassion, I also have had very low germination with impatiens (especially certain New Guinea varieties). A few years ago, I ordered multiple packs of NG Java Series Impatiens from Parks and had almost no germination.

Provided you followed the germinating instructions, most retailers and online seed sources will refund your money in the event of very poor germination.

Regards,

Ron

I have a raised bed 70' long adjacent to our porch. It is quite shady, being on the east side. I've had 7 hanging baskets full of impatiens hanging on the porch, which have reseeded and fallen into the raised bed which is lightly mulched with leaves. I've got a lot of volunteers growing there now - so I think if you broadcast the seeds onto a bed of friable soil, they should easily germinate. Of course, if you are raising them commercially, you would have a different approach.

Nancy

Overwatering and cold is death to impatiens seeds and seedlings. I wet my soil with water to which I've added damp off before I put it in the containers. Not sopping wet but thoroughly moist. Then I put a humidity hood over them and a heating pad under them. I do not water again until after they have germinated. About the third day after I have planted them I start misting the container once or twice a day. I have damp off in my water here too. Then I only water a little at a time once I take the humidity lid off. This keeps the soil moist but not wet. I planted 250 seeds this year and ended up with 241 plants.

I order my impatiens seed from stokes I like the tempo series because it has good sized blooms and it is the earliest to flower--250 seeds for a little over $7.