I looked through my seeds and all the shrubs and trees are not hardy in your zone. Too bad.
But . . . do you still have any of the Coreopsis "Creme Brule"? If yes, would you like to trade for something on my list? http://members.gardenweb.com/members/exch/bev_w

Hi Growjo,
Please look up Manitoba Maple! This tree spreads with ease over years and is almost a pest. Some people like them though and are quite popular in our prairie provinces. But I've 'dealt' with them on our country property for 37 years here in Ontario. Wish there was a fairy godmother with a bulldozer willing to take a summer to remove them all!

But as to your wish for tree seeds. I can send you a small amount of seed of the following: Syringa reticulata (Japanese Lilac), Katsura Tree, Betula pendula (Birch) and Buddleja davidii (Butterfly Bush). All will need a protected area to survive in your Zone 4 except the Lilac.

Sharon

I can send you some Carpinus caroliana seeds (aka Blue Beech, American Hornbeam, Ironwood). It's supposed to be hardy to Zone 2. It doesn't sound like you have much shade yet but it's a good understory tree for when you do. Mesic conditions are best (ie bottomland tree more than upland tree).