Can you clarify what you mean by "greenhouses" - ones that are used indoors? Maybe post a link to the product you are using or post a picture of your set-up.

You could be talking about anything from just domed trays to the huge portable greenhouse shelf units and it will make a BIG difference in identifying the problem.

As a general rule, no plants should remain contained or covered or enclosed once they germinate and most seedlings shouldn't have to be watered that often. But we need much more info please. What are the seedlings planted in? How often are you watering? Why only at night? Do you leave water standing in the trays?

Start with a review of the basic FAQ's linked below to see if they help.

Dave

Here is a link that might be useful: Growing from Seed FAQ's

Well, they are the small dome greenhouse i guess- black tray bottom with grooves, square peat pots, and plastic cover. They are planted in an organic seed starting mix, so no I have not fed them. I water them at night if the peat pots look dry. I have a grow light about one and half feet above them for about ten hours a day.

Hi!
I think you need to move the grow lights a lot closer and aim for more like 14-16 hours of light a day. The light should be 2-4 inches above the plants- a foot and a half away probably isn't doing them very much good.

Like Dave said- if you still have those plastic covers on them, they really need to come off. As soon as the seeds germinate, the covers should go or you risk damping off.

To avoid overcrowding, your best options are to either sow a litle more thinly next time or, once the seedlings come up, pick out the strongest one in the pot and cut out all the others with a small scissors. It's hard to do, but your plants will be healthier and stronger without all that competition.

Does your organic soil mix have any fertilzer or nutrients in it at all? If not, you might want to get some and feed them a diluted mix maybe two times a week one they have their first or seconds set of true leaves. Once the cotyledons are gone, there's really nothing feeding your plant-babies except you!

Good luck!

Overcrowding = you planted too close. Simple as that. Thin them as soon as you think they're strong enough to tolerate it.

Weak and falling over, 95% of the time, it's due to insufficient light. "A" grow light 1 1/2 feet above them for 10 hours a day? Unless that's a HID, that's not enough. Fluorescents should be no more than a couple inches above your plants, and you should have as many lights as you can fit over your plants. Incandescents should pretty much never be used to grow plants. It's possible, but it's just a bad idea.

Also, consider putting them on a longer light cycle. I'd recommend at least 16, and I've seen some pretty impressive results with 24.

So you are using the standard domed trays. Please note that the domes cause problems UNLESS you are planting all the same variety in the whole tray.

No way different things will germinate at the same time if you leave the dome on waiting for the late-comers the early ones are killed by damp off.

Either use separate containers and bags or tear the trays apart and plant only 1 variety in each tray. Then when some of that plant germinate it can be removed from the tray and dome and the rest can be left covered.

Domes and plastic covers are for germination only. They can kill sprouted seedlings. Once sprouted the plants need air and lots of light, not covers.

As for light, as the others have said, your light are way too far away. Fluorescent shop light kept no more than 2 inches above the top of the plants. Grow lights are not needed unless you want to spend the extra money on the.

This, as well as fertilization needs, how to transplant, etc. is explained in great detail in the FAQ's here, linked for you previously.

Dave

Thanks to you all! I will get my grow light closer, and aim for 16 hours a day.
Once they germinate, domes removed, how often should i water them?
Thanks for all your help.