@Bvangorp - you are from Chicago area, I am from the northern burbs, along the lake. The 6 or 7 oaks locally native are not very good for bonsai, really not worth collecting, UNLESS you find a really cool, interesting twisted well barked up trunk that bends and curves in the first 6 inches and is larger in diameter than a beer can. Usually if you find one like this, its roots go too deep to consider digging.
The bur oak is the local oak that has the best bark. The fissured bark of a mature bur oak is quite nice. I am raising a few whips from seed, bending and twisting them up in the hopes that in 20 or 30 years they will have both interesting shapes and good fissured bark. Right now leaves are HUGE. I believe they will come down in size as the branches develop ramification. Large leaves is a major issue when trying to work with oaks.
The second most dramatic bark of the greater Chicagoland area oaks is Quercus bicolor - the swamp white oak. This one might be more adaptable to growing in a pot and does have much more normal size leaves compared to bur oak. Definitely worth looking for in terms of collecting and or worth experimenting with as a 10 to 20 year "grow your own" project. It it fair fast growing for an oak.
If you are going to collect, late winter is one option. IF YOU LIVE NEAR THE LAKE - AUGUST is a good month. But only if you are in range of "Lake Effect" micro-climate. If you are not sure, give August a try on less valuable stock. But late winter or early spring is probably best collecting time.
Great thing about using native oaks, winter protection is ZERO. I set the pots on the ground for the winter, that is it. No mulch, nada. Bur oak is just fine. I don't have other oaks, haven't tried them yet, but I would assume the same. All local collected trees, I just set on the ground. No mulch, no trips to the well house, no burying things, to back ache, no head aches.
I do slip them out of fancy pots and put them in plastic pots. As freeze thaw can break even fine pottery.
