You dont want them comnpletely closed up, there should be air circilation.

The wide open ones, I think, are usually after they're sprouted and its warmer close to being platned out.

I am new too, but think that the purpose is to have a 'terrarium effect', thereby not needing to water over the winter and spring time. From what I see, the wide open containers are pictured after spring has arrived and germination has happened. Then, they need space to grow.

I would think the containers wouldn't need to be opened until the green growth reaches the top ---- or occasionally when they need a breather.

I'm a newbie too but I think one of the advantages of having the smaller ventilation hole to start (before germination) is to prevent the seeds from washing to the outside edges of the container if you get a heavy spring rain.

Daffodillady,

There are many things that wsing accomplishes.

For those of us without a greenhouse and lights in the basement, it provides us with an acternative which doesn't cost an arm and a leg and uses rescources which are readily available to us.

It also does provide protection from critters and extreme weather, mainly heavy rains since your seeds don't end up in Timbuktoo.

It does provide a bit of a greenhouse effect no doubt. This particular aspect has to be watched when the outside temperatures start getting warmer, wether your seeds have germinated or not. I stuck a thermometer inside my containers in year two and discovered that when the outside temps are around 18C, inside the containers the temps are 28C. That's a big difference and it tells me that when outside temps start reaching anything above 15C, I have to start making bigger holes for aeration whether things have germinated or not.

Sometimes things take longer to germinate and because of the weather warming up, you still have to take the covers off. Else you will have fried seeds and no germination.

For this reason, Carmen, containers do need to be opened before the green reaches the top.

I start opening as soon as they have germinated, bit by bit. Sometimes I take a chance and do it more quickly, but I now know which plants can take it and which ones can't. It's all a matter of having done this for a few years. You get to know what works and what doesn't.

As an example. My DD sowed some Bachelor Buttons in Feb. in 2006. They germinated March 26th. During the first week of April, we bagan taking the cover off her little tub full of sprouts. On April 9th, the cover was taken completely off for the day. It was a nice warm one. The intention was to cover again before night fell, but we forgot. The cover was still off on April 11th when we had an ice storm which dumped 2 inches of ice pellets on those babies. I realized this too late, and left things alone. Two days later, I checked the container fearing the BBs were gone.

They weren't!!!! Those are tough babies. In late May we planted the strongest BBs in the gardens ever!! :O)