I wouldn't worry about the natural gibberellins in the soil the plant and seed pod should prepare the seed when it is ripened with any gibberellins it should need to germinate. From what I have found your soil should be fine for this plant. With all the extra decomposed organic matter that you are cleaning up (leaves and bark) I would just work that into the soil where you want to plant. This natural organic matter is great for nutrients and soil health. Here is a web page that can give you some information on starting from seed.
http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Cornus+canadensis
Seed - best sown as soon as it is ripe in a cold frame or in an outdoors seedbed if there is sufficient seed[80, 113]. The seed must be separated from the fruit flesh since this contains germination inhibitors[80, 164]. Stored seed should be cold stratified for 3 - 4 months and sown as early as possible in the year[164]. Scarification may also help as may a period of warm stratification before the cold stratification[80, 164]. Germination, especially of stored seed, can be very slow, taking 18 months or more[164]. Prick out the seedlings of cold-frame sown seeds into individual pots as soon as they are large enough to handle and grow the plants on for their first winter in a greenhouse, planting out in the spring after the last expected frosts.

Here is a link that might be useful: Plants for a future

Apermann,
Thanks for the info. But I've seen so many different references for the germination of this seed (including the one you sent me I think), that I really don't know what is the best way. I bought the seeds through a website in Ontario and their instructions say that GA3 is required and to sow for 3-17 weeks at 20C (68F for you). And through reading the forums on the GW, winter sowing will also work apparently. However, I'm guessing I'm a little late for that (or am I?...can anyone comment?). I will most likely end up just sowing them where I want them to come up and see what happens. I'm not sure if I'm patient enough to wait until next year to see them come up, but I might not have a choice. If I knew where to find some GA3 (I'm not having any luck), I might try it, but I have no idea where I would get it in Canada outside of a lab. Anyone know?
Thanks again.

You can get ga3 from Peaceful Valley Farm Supply. It's costly. One method I have used to germinate really tough seeds that normally need cold stratification is soaking in cold water that is changed for fresh daily for two weeks, then sow. I have done this with seeds like mandrake, belladonna, and some aconites and gotten germination after about 2-3 weeks. It doesn't work for every seed by a long shot, but it is definitely worth trying for this type of seed. It's a lot faster than cold strat, that's for sure. The idea is that it duplicates snowmelt, which leaches the anti-germination chems in the seedcoat. Actually, I am trying it on a bunch of new seeds right now, including Acinos alpinos, a couple aquilegia species, and some other stuff.

Interesting...very interesting. Do you sow them indoors or directly outside?...or does it just depend upon the seed?

GA3 isn't required to germinate the seed. The seed normally requires warm stratification to mature the embryo, followed by cold stratification to break dormancy. GA3 can help to reduce these requirements so the seed is easier to germinate.

Nicking, soaking, etc cannot substitute for these types of dormancies, they are a way to get past tough seed coats which would normally be broken by animal/bird digestion, fire, freeze-thaw cycles, or simple physical damage over time.

If you have a lot of the Cornus seed, a few seeds might germinate relatively quickly without any special treatments.

You can sow them outside or inside afterwards. I usually am working with plants I want to have ready to go once the frost is over and sow them inside about a month before the last frost date.

From what I've read about GA-3, it's not a common component in average soil, wild or garden, otherwise you'd have a lot of plants dying from growth acceleration. It's also not provided by the mother plant (nor any of the gibberelins). Some other gibberelins are natural in some soils, though, like GA-7, which bloodroots require for germination. GA-3 generally isn't a requirement for germination for most plants that will germinate with it, with the exception of a relatively small number of species (like some Andean violas). Cornus canadensis, from what I've read, like shrubs_and_bulbs said, does not require it, but it will accelerate germination.

That said, I hae to say that I'm having fun with it so far. I had gentiana luteas germinating well with it, as well as some trillium grandiflorums. It is a bit hard to find, though. JL Hudson is a good supplier in the US, and Gardens North in Canada.

Magus,
I just wanted to say thanks for the source info. I actually bought the seeds from Gardens North. I wish I knew they had GA3 but they don't advertise it on the website.
I'm trying a couple different things with the seeds right now.....nothing I'm expecting to work though.
Guess I'll just call them back...