Vermiculite in a plastic ziploc bags simply allows you to see when the seed has germinated. Many clematis seeds produce the root first but then wait a long period of time before sending out leaves (sometimes another year or another set of season changes). The vermiculite/bag method allows you to see if the root has been produced.

It's also a great space saver - one small bag versus one large pot.

Others think the increased oxygenation and high moisture content of the enclosed bag may speed germination as well, though I've not seen proof of that yet.

I agree, space is my biggest factor.

Also more consistant moisture. I have tried in the soil method and can not manage to keep an eye on the pots. Therefore the soil starts to dry out. Once a seed gets started it can not dry out completely otherwise death occurs.

I can start many bags of various things, not just clematis and save an incredible amount of space. I just string a string across the window or lighted area and pin them up. I can see at a glance if there is any growth without fiddling around with pots, covered or not.

It is my preferred method of which I can say I have great success. Especially important when only a few seeds have been produced.

Dana

There are definitely pros and cons for both the vermiculite in a baggie method or the seed starting mix in a pot which is then enclosed in a ziplock bag. I like the vermiculite in a baggie method because it is a tremendous space saver. If you are not sure about your ability to transplant seedlings that have just germinated and are essentially just roots with or without top growth, then the method may not be for you. I also go round and around with trying to decide how much moisture I need in the baggie with the vermiculite. Sometimes I add too much water and then either open the baggie to get the excess moisture to evaporate or will dump everything out to let it dry out some more or even just add more vermiculite. Another draw back that I have seen is being able to determine when things have germinated since the seeds blend in with the color of the vermiculite--especially things that only put out roots but no top growth for the first season or so. I also have had mixed results with leaving seedlings that have just produced roots in the baggies versus going ahead and taking them out and potting them up. I know Helen who uses the baggie method has had similar mixed results. I also have issues with rolling the vermiculite around in the baggie trying to see if I have germinations--I have broken off some roots trying to ascertain whether there have been germinations, but then again I can be a klutz at times with various things! LOL

To over come the issue with being able to see the seeds in the vermiculite, this year I am trying using some of the seeds in baggies with perlite since the white color of the perlite allows the seeds to be easily found in with it due to the color difference. Here is a picture of seeds in the perlite. Sorry about the picture quality but you can definitely see the dark seeds versus the white perlite in the baggies.
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Once the seeds germinate and the roots get long enough and/or the embryonic leaves appear, the seedlings are easy enough to see. Here are some Hanajima seedlings that germinated while I was away on vacation. There were six seedlings that germinated and only one of them had top growth that was readily visible. The others still had the seed coat over the leaves and the embryonic leaves has still not come out of the seed coat. Luckily however their roots had gotten long enough that I was able to see them. All six have been transplanted into pots.

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Here are two Hanajima seedlings that germinated about a month or so ago in the baggie/vermiculite. When I left on vacation, the two embryonic leaves were the only things showing, now you can see the first true leaves have formed and they are well on their way.
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The seeds in a pot in seed starting mix that is then enclosed in a baggie method is very easy because you just pot them up as you would any other seeds, water them in well, allow the excess moisture to drain out and then place the pots in ziplock bags. You basically can ignore the pots and not look at them for a week or so at a time and even if you have germinations, you can leave them in the baggie for a few weeks (believe me I have done this by just forgetting about them and then realizing that I had plants up over a couple of inches tall!) and the plants are generally going to be alright as long as there is bright and indirect light available. Then the pots can be removed from the baggies and you can 1) allow the plants to grow on until the first true leaves develop and transplant them then or 2) gently coax the seedlings out of their pots and pot them up on their own. The pots with the ungerminated seeds can then just be placed back into the baggies to await more germinations. This method does take a whole lot more space depending on how many pots you are using. In my climate, trying to find a cool place for these pots in the baggies to rest over the summer is a real job. In the fall thru early spring, they can be left in the garage since it doesn't heat up. In the summer however I have to find a place in the house where my cats won't disturb them since the garage can get very hot and I am afraid of this causing the seeds to rot if I left them there. I have considered placing the pots under the house in the crawl space since it stays cool there over the summer, but there are definite disadvantages to that including having to crawl under the house to periodically inspect the pots and the lack of sunlight under there in case some of the seeds germinate and I forget about them.

Either way there are definite advanatages and disadvantages of starting seeds either of these ways. You just have to decide which is better for you and the best way is just to give it a go both ways and see which works for the conditions you have.

WOW! The information you all have given is so very helpful. Think I will try several methods and see what works best