When the berries are bright red, you can pick them and find the seed inside. Usually the birds eat the berries and pass the stained seeds out. It takes years to get a mature tree from seed. Kousa dogwood seems to grow faster than K. florida from seed. Kousa will produce a 3 foot tree in about 2 years from seed, in the right conditions. Dogwood seeds have to overcome a double dormancy to germinate (2 months warm period, followed by a 3 month cold period, followed by a warm period), and they can take up to two years to grow. These are best winter sown by Mother Nature :)

Tony, are you familiar with the Winter Sowing forum? We sow seeds in covered containers and put them out in winter to let Mother Nature take care of them. Seeds that need warm/cold/warm are going out NOW.

Sow your seeds in a large pot with drainage holes and cover with plastic. Make holes in the plastic to allow rain and snow in to keep your seeds moist. The plastic keeps the critters from disturbing or eating your seeds. Put your container outside and let Mother Nature do her thing. You can pretty much forget about it unless you go through LONG periods of no rain or snow. You don't want your seeds to dry out during a critical point of germination. You want damp but not soggy soil in your container.

In your zone, you have plenty of warm before the winter. In the spring your seeds should sprout nicely.
I have grown many trees and shrubs using the Winter Sowing method and it works great.

Thank you both for all the excellent information. It is most appreciated. Tony